an ecosystem approach to fisheries...

Aquaculture amp Fisheries Group Wageningen University

2112011

1

Paul van ZwietenFisheries Data Collection and AnalysisMonday 7 November

An ecosystem approach to fisheries information

Devising indicators of fisheries resources

Introduction

My background Small scale fisheries information needs for fisheries

management in datapoor situations

Papua New Guinea Southern Africa freshwaters

Coastal fisheries Indonesia Thailand Vietnambull Red River Delta Nam Dinh province

bull RESCOPAR Ca Mau province East Kalimantan

Lake Victoriabull Impacts eutrophication and fisheries on Nile Perch stocks

BestTuna projectbull With WWF ndash in search of mechanisms to better manage tuna stocks in Coral Triangle area

bull Market based mechanisms


2112011

2

Today ndash sermon and system analysis

Introduction Approach to management

Focus on information needs for decision making

Information understood by all involved in managementbull Role of fisheries scientist

A system approach Indicators

Tuesday Thursday

Tuesday is a trendy day

Trends and information value of indicators

Trends and causation ndash stock assessment with paper and pencil

Trends and own data ndash catch and effort

Thursday is an assessment day

Models introduction and two biomass dynamic models ndashcatch and effort

Indicatorsbull Three simple indicators

bull Stock assessment with indictors based on catch and effort


2112011

3

Part 1 Sermon

Management cycle Quantified objective

eg Y=50 kg ha1 yr 1

Evaluation

eg Y too low overfishing

Management measure

eg 30 reduction in number of boats

Information

monitoring catches

eg Y=30 kg ha1 yr 1

Feedback

Userstakeholder preferences

Biological potentials and constraints

Resource use problem


2112011

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Participation

Writing history together

Users and information needs changing role of

science in evaluations


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5

Perceptions on stock sizes of researchers and fishers

1970 1975 1980 1985 1990 1995 2000 20050

20000

40000

60000

80000

100000

Exp

loita

ble

stoc

k (to

nnes

)

sole

Catch ratesStock size

Photo Van Densen

More inclusive stakeholder involvement the information

challenge

Fishers Managers

Greens TradersSupermarkets general

public

DataInformationKnowledge

Role of science

Measurement Historical data Sensitivity Theoretical basis

B F important

Responsiveness to action

Costs

Total pressure (C f F) important

Related to quality notions of good practice

Selectivity important (q) - labels

Experts

Related to experience spaces

Catch efficiency (Cf q) important


2112011

6


eg Y=50 kgha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kgha1 yr 1

Feedback



Resource use problemFrom values hellip

hellipto techniqueshellip

hellipto valueshellip

Role of fisheries biologist experience for all

Knowledge

Information

Data

Structuring

Experience learning

Evaluation sensemaking


2112011

7

Evaluative capacity ndash social learning

Writing history together Fishers managers others

Management objectives ndash information needs

Production planning ldquoFeed the peoplerdquo

Fisheries Management ldquoSet levels of resource usagerdquo

Nature conservation ldquoRetain the integrity of naturerdquo

bull Biological

bull Social and economic


2112011

8

Only 2 biological questions in fisheries management

How much = Fishing pressure

bull Effort (f )

bull Catch (C)

How = Fishing pattern

bull Catchability (q )

bull Selectivity (s )

How much

How

Why fisheries (stock) assessements

Optimising catches ndash how much

Long term sustainability

Given variable stock sizes

Sharing arrangements catches ndash how much how

Between fishers

Between countries (eg migratory stocks shared seas and lakes)

Assessing sustainability of fisheries ndash how

Total pressure

Selectivity of catches size communities incl fish birds mammals

bull Tracking and tracing

bull Labelling

Habitats


2112011

9

Focus management and environmentalists on human impact and

control Fishers refer to natural influences Dispute

Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY

Main objective to ensure optimalsustainable harvest

Main measure control of fishing effort


2112011

10

Control of targeted sizes

Bio

mas

s

Length (Age)

Selectivity curve small hook

Selectivity curve large hook

Available biomass Available

biomass

Control of pressure reference level (MSY)

Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited

Maximum Sustainable Yield


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11

Fisheries management options

Input controls Ban of fishing techniques (q) Maximummin mesh size (q) Change in gear construction (q) Days at sea (f)

Reduce number of gears (f)

Closed areas (f)

Closed seasons (f)

Protection habitats (fq)

B

C F = fq

Output controls (C)

Total allowable catch (TAC)

Individual Transferable Quota (ITQ)

Target specific specieslengths

C = FB

That is all Any available or

conceivable regulation can be reduced to the two terms C and F with goals defined on B

All are through regulating fishing effort

BMSY SSBmin SSBpa Cf MSY

M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd

HolisticBlack box approach

Analytical approach

Fisheries science ndash information evaluation


2112011

12

Data needed for assessment general

Basic data from the fishery

CatchperUnit Effort (tonnes numbers)

Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)

Spawning (recruitment maturity stages areas)

Age

Natural Mortality

Trade offs in multispecies communities ndash no free lunch

MMSY =

Target LimitStay clear off


2112011

13

Goals data collection needs linkages

Production planning trade Catch Input ndash labor vessels No link

Fisheries management Catch and effort linked By commercial species

Conservation Catch and effort linked Selectivity All species Habitats ecosystems

Increase in

- Resolution

- Linked data

- Costs

Ecosystem based management

Ecosystem based management What is that

Change in information base Fisheries Science = heavy investment in population dynamics Ecosystem = interaction between organisms with each other

and the physical environment New questions arise on habitats and nontarget organisms

Not clear how the fisheries ldquohowrdquo and ldquohow muchrdquo questions can be dealt with Focus on more generic measures as MPArsquos (keeping a bank)

Focus on clarity of information for all involved what info is needed


2112011

14

Biomass

Models ndash Indicators references and the long view

Fishing mortality = CB

Recruitment

Growth

Natural mortality

Indicator approaches ndash system stakeholder

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science

Part 2 a system approach


2112011

16

Goal

Apply a systems approach to fishery information ndashdevising indicators System

bull Understand the role of environment and fishing as sources of population regulation (mortality)

Species Stocksbull Understand that different species have different resilience to fishing

Selectivity ndash Catch and effortbull Understand consequences of (un)selective fishing on fish communities

bull Understand the characteristics of small scale fisheries

bull Understand the potential (and drive) to stabilise catches

Africa diversity of freshwater and marine systemsFreshwaters bull Rivers Nile Orange Congo Zambezi etc

bull River floodplains Niger Congo Zambezi Kafue Pongolo etc

bull Exorheic swamps Sudd Bangweulu Kamulondo Cuvette Centrale Luapula Shire Malagarasi Lukanga

bull Endorheic wetlands and lakes

Chad Okavango Chilwa Rukwa

bull Man made riverine lakes

Kariba Cabora-Bassa Volta Nasser Kainji

bull Shallow lakes open drainage

George Edward Kyoga Malombe Mweru

bull Large deep lakes Tanganyika Victoria Malawi Turkana etc Marine systems bull Upwelling areas Coastal East and Souther Africa

Mauretania Namibia bull Estuaries River mouths bull Tidal flats Banc drsquoAacuterguin bull Continental flats banks Coastal Mozambique Sofala bank bull Coral reefs Red Sea Coastal Islands Tanzania Kenya bull Seemounts bull Open ocean


2112011

17

Two important indicators

Catch

Effort

Fopt

C = fqB

Relation productivity amp number of fishermen

y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16

Density (fisherskm^2)

Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702

Victoria 1990 Victoria 20024

Volta Kainji

Average annual catch rate for African fishers = 3 tonyear irrespective of system


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18

Information needs towards indicators

Systems differ

in productivity

In variability in productivity

in species communities

in effort dynamics

Contextualising fishing patterns and outcome

Scaled indicators

Systems approach ndash sources catch variability

Physical forcing drivers Rainfall water level nutrient pulsing

Climate el Niňo cycles nutrient upwelling

Landuse runoff rainfall nutrient loading siltation habitat change

Ecological spatial heterogeneity

Fish communities species attributes

Exploitation fishery characteristics

(Co)management structure organisation goals


2112011

19

System approach ndash a theory

Physical environment

Ecosystems

Fish communities

Fishing techniques

Fisheries management

Economics

Administration

Env

ironm

ent

Ecosystem drivers ndash pulsed stable


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20

Okavango ndash highly pulsed system

Fluctuating environment Unpredictable

Mortality = density independent high often catastrophic

Population = variable in time less than carrying capacity

Freshwater Lake MalawiVictoria ndash constant system

Stable environment predictable

Mortality density dependent low constant

Population size constant in time around carrying capacity


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21

Marine Red River Estuary Variable Predictable

What are the dominant life history strategies


Marine Komodo Coral Reefs Highly Stable Predictable


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22

Drivers ndash waterlevels ndash nutrient pulsing

Scale of variation

Time Process

decadal community

annual stocks

seasonal year class

Monthly industrial catch rate clupeids lake Tanganyika

1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small

Drivers ndash wind stress ndash nutrient upwelling

decadal annual seasonal variation


2112011

23

Drivers ndash weather patterns ndash nutrient upwelling

Normal pattern

Effect=1-2 years signal clear Yes

El Nino pattern

Drivers Eutrophication Lake Victoria eutrophication through increase nutrient loading related to landuse


2112011

24

Assignment 1 Drivers Your situation

What type of system

stable ndash pulsed

What drivers are important climate wind waterlevel droughts upwelling eutrophication land

use change

What indicators needed for assessment

What datainformation is needed to monitor longterm developments

Who haswhere is this information available

Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25

A Lindeman pyramid illustrating

a fish community

Size

Biomass

The biomass-size distribution important indicators in both single species and community studies

A fish community

Fish communities ndash size biomass trophic groups

Size of individual fish

Competition

Predation

Detrivores Herbivores Zooplanktivores etc

Piscivores


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26

Tilapia ndash Oreochromis mossmbicus detrivore

Small Clupeidae zooplanktivores

Lake Tanganyika

bull Limnothrissa miodon 17 cm (top)

bull Stolothrissa tanganicae 10 cm

Lake Mweru

bullMicrothrissa moeruensis 6cm


2112011

27

Small zooplankton ndash from eutrophic Tjeukemeer

Nile Perch from Lake Victoria Piscivore


2112011

28

Haplochromis Species From Nile Perch Stomachs

Lake Mweru ndash a fish community

Length (cm)

MolluscInsect

Cyprinidae (5)Cichlidae (3)Mormyridae (5)Bagridae (2)Mochokidae (3)TylochromisOreochromisClariidae (2)Serranochromis (2)HydrocynusSchilbeidae (2)AlestesOthers (50)

Molluscivore

MicrophytovorePiscivore

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


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29

Size

Biomass

Multispecies fisheries Mweru ndash all sizes and trophic

levelshellip

hellip and all levels are fished

Assignment 2 Fish communities my situation

How many different species are there in the fishery

Which are most important

What biomass (large ndash medium small)

What maximum sizes (large ndash medium ndash small)

What trophic levels (piscivores herbivores benthivores)

What spaces (pelagic demersal migratory)

Draw the most important species into a biomass size spectrum

order them by maximum size trophic level and space (pelagics on top demersal on the bottom)


2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent

Fish species ndash resilience to fishing

Change in Fish Communities Fishing Environment


Competition

Predation


Piscivores

Fishing pressure


2112011

31

Catch development in a multispecies fishery

Catch

Fishing effort

Fishing down process ndash example Oueme river

Succession of species

black disappeared lt1965

hatched seriously reduced

peak yields around 10000 ton in rsquo50rsquo60ies

Why are some species less resilient to fishing


2112011

32

time

N

Population growth

Logistic population growth dNdt=r0N(1NK)

K carrying capacity (Nmax)

r0 steepness of the increase

Life history strategies r and Kselected species

rselected species small shortlived high reproductive rates (sardines)

Rapid growth and development Early maturation many offspring with low survival rates Population size below carrying capacity Minimal parental careoffspring Use unpredictable or unstable habitats Abundance varies greatly in time and space Generalists limited niche or trophic specialisation Resources rarely limiting (no competition) Wide dispersal good colonisers rapid response to disturbance Selection for productivity

Anchovy Max age 3-4 years

r=43 Population doubling time lt15 months


2112011

33


Kselected species large longlived lower reproductive rates (sharks rays)

Slow growth long life span Fewer offspring with higher survival rates Population size operate near carrying capacity (K) Use more predictable or stable habitats Parental care is common Abundance stable over time Specialists efficient users of a particular environment (niche

specialist) Resources often become limiting competition Poor colonizers of new or empty habitats (no dispersal) Selection for efficiency (competitive ability)

Hammerhead sharkMax age 14 years

r=08 PDT = 45 ndash 14 years

Not the complete story fish are more plastichellip


2112011

34

Three basic life history strategiesGrowth

(population)

SurvivalFecundity

Opportunist strategist small shortliving early maturing fish asymp rselected

Periodic strategist high fecundity longer lifespan

Equilibrium strategist medium size some parental care few but larger offspring asymp Kselected

Winemiller and Rose 1992

King and McFarlane 2003

Intermediate strategist

Opportunistic strategist

Early maturing fish frequent reproduction extended spawning period rapid larval growth high population turnover rate (PB = Z = r) eg mosquito fish Marginal habitats (eg like terrestrialaquatic ecotone)

More common in tropical freshwaters

Rarely exploited (small size) otherwise no management needed but to protect founder populations


2112011

35

Equilibrium strategist

Large adult body size parental care behaviour

Tropical (stable) fresh waters coral reefs (K)

Density dependent processes and resource limitation

Management maintenance of a productive environment and a healthy adult stocks

Periodic strategist

Maximises age specific fecundity at the expense of juvenile survivorship

If favorable conditions for immatures = periodic synchronous reproduction in phase with periodicity of large numbers

of small offspring

Weak stock recruitment relationships

Management maintain a critical density of adults stocks Protect spawning season andor habitat


2112011

36

Fishbase species resilience to fishing pressure life

history

Three categories of species resilience to fishing Very lowlow ndash medium ndash high

Based on lifehistory characteristics reproduction feeding and spatial behavior

Through the effects of survival fecundity and growth

trophic position

migratory behaviour

See FishBase wwwfishbaseorg

Lake Mweru ndash Mormyrops anguilloides

Resilience Low

Minimum population doubling time = generation time 8 years

Life span 24 years

Max length 150 cm

Lengthage2at2maturity 65 cm 5 years

Trophic level 36

Migratory no

Intermediateperiodic


2112011

37

Lake Mweru Hydrocynus vittatus

Resilience Mediumlow

Generation time 3 years

Life span 11 years

Max length 105 cm FL

Lengthage2at2maturity 42 cm 2years

Trophic level 44

Migratory yes spawning migrations

Periodic

Lake Mweru Oreochromis mweruensis

Lake Mweru

Resilience High

Minimum population doubling time lt 15 months

Life span 11 years

Max length 40 cm

Lengthage2at2maturity 15 cm 1year

Trophic level 20

Migratory no

Intermediate opportunistc


2112011

38

Lake Mweru Microthrissa moeruensis

bull Z = PB ~ 5 ndash 7

Resilience High

Generation time 6 months

Life span 25 years

Max length 5 cm

Lengthage2at2first maturity 3 cm04 year

Trophic level 20 ndash 30

Migratory no

Lake MweruOpportunistic

Assignment 3 Resilience to fishing my situation

Use main species in the fishery in assignment 2 (choose at least three) What is their productivityresilience to fishing

What characteristics are used to assess thisbull Size longevity reproduction feeding spatial behaviour

What is the turnover time (PB = Z = r)

Use Fishbase to find out these characteristics What indicators

What datainformation is needed Who haswhere is this information available


2112011

39

Fishing pressure fish communities and system stability


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force

Drivers climate wind waterlevel droughts upwelling eutrophication

Fish Communities ndash population regulation

Constant systems

Pulsed systems

Population regulation

nonselective catastrophic mortality

(environmentdominant)

selective mortality (predation competitiondominant)

environment determines prevailing mortality pattern


2112011

41

Most ecological processes and life history traits can be related to the prevailing mortality pattern

Life history and natural selection

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8

Relative age (years)

Abu

ndan

ce (

N)

but large fish have more eggs

50 cm = 1 mill eggs 100 cm = 16 mill eggs

Age at 50 maturity

Young fish are supposed to die only a fraction will spawn


2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)

is almost exactly oppositeSelectivity predation versus fishing

Management promotes harvesting patterns that is opposite to what most fish stock are naturally adapted to

effort

Age and size structure changesunder selective fishing to younger and smaller individuals

A sign of fishing hellip


2112011

43

Median age-at-maturation of Northeast Arctic cod (Joslashrgensen 1990 Jorgensen et al 2007 Science Conover et al )

and this is what happens

Fishery induced evolution (nr species)

Maturity lower age (6)

Maturity lower size (7)

Reduced growth (6)

Increase fecundity (3)

Loss genetic div (3)

Leading to lower yields

Small

Random

Large

Increased mortality on

Mean individual weight at age after 4 generations

Evidence Size selection (Growth)

= genetic changes

After Conover and Munch 2002Atlantic silverside Menidia menidia max age=2 years R= PDT lt15 months r=58


2112011

44

Effect of sizeselective fishing (Yield)

Trends in average total weight harvested across multiple generations of size-selective exploitation

Mortality on

Size selective fishing with large mesh sizes on adults We are deliberately pushing stocks to genetically

stable smaller sizes

Small

Random

Large

The rK selection principle the effects of selective

fishing

Age (size)

Abu

ndan

ce (L

og N

)

Slope = total mortality rate Z = r

Increased juvenile mortality= K-selection

Increased adult mortality= r-selection

r-selection Unstable environment abiotic mortality ndash non-predictive non-selectiveK-selection Stable environment biotic mortality (predation) ndash predictive size selective


2112011

45

Abundance size spectra

Abu

ndan

ce

Size

The distribution of abundance by size follows regular patterns

slope steepens when large fish removed

phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5

Rice amp Gislason (1996)

Trends in size-spectrum slopes of the North Sea

Fishing effects on community sizestructure


2112011

46

Question

How do you fish a multispecies community

Selective ndash Targeting large sizes with single gears

Unselective ndash Targeting all sizes with many gears

Multispecies community

How should it be harvested

What should be minimum mesh-size


2112011

47

Selective fishing will change the slope

Biomasssize distributions

Example from lake Kariba Zambiawhere fishers are using illegal smallmeshed nets

The system remains unchanged except everything is less

Kolding et al 2003

Parallel slopes only intercept lower


2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)

Fishing down the food web

Example from Lake Volta Ghana

The whole fish community is targeted highly pulsed system

highly dynamic fishery (spatial temporal movements fishermen)

27 fishing methods

25 kgday

74 species utilized

All trophic levels utilized by combining gears with specific trophic profiles 1 2 3 4 5Trophic level

Gears in the fishery ( species sample size)

Van Zwieten et al 2008


2112011

49

Is nonselective fishing bad

There is no empirical evidence

On the contrary we know that selective fishing is bad but we still advocate it

But how do we impose gear mesh and size restrictions in a multispecies fishery

The optimum fishing pattern is un-selective How much

How

Is fishing down the food web bad

Where is the highest production

Sohellip what is the best fishing pattern

What if we fish everything

A non-selective harvesting pattern is ecosystem conserving

The system remains intact but everything is less

This means fishing down the food-web


2112011

50

Indicators ndash biomass size distribution


Biomass Unexploited Population = Blt40

Maximum length = Lmax10

Fishing pressure

Mean length exploited population = L5

Biomass Exploited Population = Bgt40

Mean length total= Lmean

Intercept = Iasd

Assignment 4 Fishing down my situation

Characterise your fishery Single species single gear ndash multigear

Specific target species ndash all species are targeted (multispecies)

Specific size ndash all sizes (quantify)

Is there a shift from large specimen to small

Is there a shift from large species ndash to small Is there a shift in trophic level

What information is needed What indicators

Where to get this information


2112011

51

Dynamics of fishing ndash stabilise catch variability


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent

Diversity in methods ndash small units adaptive

Hook and line fisherman

Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52

Labor intensive beach seining on demersals

Small fish common Chilimira seine small pelagics


2112011

53

Innovative Nkacha seine small demersals

Unevenly distributed ndash important gears lake Mweru


2112011

54

Highly mobile ndash movement fishermen Lake Malawi

movement one fisherman in 6 months

SE Arm of Lake Malawi

Characteristics of smallscale fisheries

Small units simple processing small scale trading

Methods diverse innovative labor intensive

Opportunistic adaptive

Large subsistence element (small fish)

Unevenly distributed highly mobile


2112011

55

Fishing mortality (F)

number of units

efficiency

Effort (f)

Catchability (q)Fishing mortality (F)

More of the same

Decreasing numbers = management

Better methods = Increasing efficiency

=development

So while we both lsquomanagersquo and lsquodeveloprsquo the fishing mortality stays the same

Uh

Tradeoffs Economic efficiency vs employment

opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)

Quantity (tons) Fishermen (1000) Catch (tons) per fisherman

Total catch numbers of fishers amp catch per fisherman in the Norwegian fishery 1945-2005

Effort (f) decreases while CpUE increases because catchability (q = efficiency) increases


2112011

56

Assignment 5 Dynamics fishery ndash my situation

How has fishing effort developed over time In terms of numbers (fishermen boats)

In terms of gears bull Types

bull Active ndash passive methods

In terms of spatial distribution

In terms of trophic levels

What informationdata needed What indicators

Who haswhere is this information

Goal

Apply a systems approach to fishery information ndashdevise indicators System



bull Understand r K principle

Selectivity ndash Catch and effortbull Discuss the consequences of selective and unselective fishing on fish

communities



2112011

57

Summary All species and systems ndash important sets of

indicators

Effort (numbers types)

Species (composition in catch)

Catch (by species total)

Catch per unit Effort (~relative biomass)

Length (in catch at maturity)

Drivers (as explanatory factor)

copy Wageningen UR

End hellipbeginning


2112011

58

Summary environment species resilience management Life history strategy Opportunistic Periodic Equilibrium Environment Temporally stochastic

with small-scale patches

Seasonal with large-scale patches

Stable with fine-scaled spatial variation

Demographic trade-off 1 age at maturity 2 fecundity 3 juvenile survivorship

low low low

high high low

high low high

Demographic character Maximise (re)colonising capability of habitats over small spatial scales

Maximise age-specific fecundity spreading of reproductive effort over many years andor large areas

Maximise juvenile survivorship in resource limited density-dependent environments

Life history traits - size - age at maturity - size at maturity - clutch size - egg size - larvalYOY growth - reproductive season - parental care

Small Early Small Small Small Rapid Long No

Large Delayed Mediumlarge Large Small Rapid Short No

Smallmedium Delayed Medium Small Large Slow Long Yes

- Maintain critical minimum spawning biomass

- Maintain appropriate age structure (including large specimen)

- Maintenance of adult stock

Primary management objectives

- Protection against large scale or chronic perturbations that eliminate key refugia in space and time

- Spatial refuges directed at adult stock (including spawning habitats and migration routes)

- Maintain integrity of adult habitat

Environment

Demographic trade-offs

Life history traits

Management objectives


2112011

2

Today ndash sermon and system analysis

Introduction Approach to management

Focus on information needs for decision making

Information understood by all involved in managementbull Role of fisheries scientist

A system approach Indicators

Tuesday Thursday

Tuesday is a trendy day

Trends and information value of indicators

Trends and causation ndash stock assessment with paper and pencil

Trends and own data ndash catch and effort

Thursday is an assessment day

Models introduction and two biomass dynamic models ndashcatch and effort

Indicatorsbull Three simple indicators

bull Stock assessment with indictors based on catch and effort


2112011

3

Part 1 Sermon


eg Y=50 kg ha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kg ha1 yr 1

Feedback





2112011

4

Participation





2112011

5


1970 1975 1980 1985 1990 1995 2000 20050

20000

40000

60000

80000

100000

Exp

loita

ble

stoc

k (to

nnes

)

sole


Photo Van Densen


challenge

Fishers Managers


public


Role of science


B F important


Costs




Experts




2112011

6


eg Y=50 kgha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kgha1 yr 1

Feedback







Knowledge

Information

Data

Structuring

Experience learning



2112011

7







bull Biological



2112011

8



bull Effort (f )

bull Catch (C)




How much

How






Between fishers



Total pressure



bull Labelling

Habitats


2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

3

Part 1 Sermon


eg Y=50 kg ha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kg ha1 yr 1

Feedback





2112011

4

Participation





2112011

5


1970 1975 1980 1985 1990 1995 2000 20050

20000

40000

60000

80000

100000

Exp

loita

ble

stoc

k (to

nnes

)

sole


Photo Van Densen


challenge

Fishers Managers


public


Role of science


B F important


Costs




Experts




2112011

6


eg Y=50 kgha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kgha1 yr 1

Feedback







Knowledge

Information

Data

Structuring

Experience learning



2112011

7







bull Biological



2112011

8



bull Effort (f )

bull Catch (C)




How much

How






Between fishers



Total pressure



bull Labelling

Habitats


2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

4

Participation





2112011

5


1970 1975 1980 1985 1990 1995 2000 20050

20000

40000

60000

80000

100000

Exp

loita

ble

stoc

k (to

nnes

)

sole


Photo Van Densen


challenge

Fishers Managers


public


Role of science


B F important


Costs




Experts




2112011

6


eg Y=50 kgha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kgha1 yr 1

Feedback







Knowledge

Information

Data

Structuring

Experience learning



2112011

7







bull Biological



2112011

8



bull Effort (f )

bull Catch (C)




How much

How






Between fishers



Total pressure



bull Labelling

Habitats


2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

5


1970 1975 1980 1985 1990 1995 2000 20050

20000

40000

60000

80000

100000

Exp

loita

ble

stoc

k (to

nnes

)

sole


Photo Van Densen


challenge

Fishers Managers


public


Role of science


B F important


Costs




Experts




2112011

6


eg Y=50 kgha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kgha1 yr 1

Feedback







Knowledge

Information

Data

Structuring

Experience learning



2112011

7







bull Biological



2112011

8



bull Effort (f )

bull Catch (C)




How much

How






Between fishers



Total pressure



bull Labelling

Habitats


2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

6


eg Y=50 kgha1 yr 1

Evaluation


Management measure


Information

monitoring catches

eg Y=30 kgha1 yr 1

Feedback







Knowledge

Information

Data

Structuring

Experience learning



2112011

7







bull Biological



2112011

8



bull Effort (f )

bull Catch (C)




How much

How






Between fishers



Total pressure



bull Labelling

Habitats


2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

7







bull Biological



2112011

8



bull Effort (f )

bull Catch (C)




How much

How






Between fishers



Total pressure



bull Labelling

Habitats


2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

8



bull Effort (f )

bull Catch (C)




How much

How






Between fishers



Total pressure



bull Labelling

Habitats


2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

9



Catch

Effort

Nature

Fishing community

Researcher

Size

Objective measure

Total effort

Total catch MSY




2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

10


Bio

mas

s

Length (Age)




biomass


Cat

ch (

= Y

ield

)

Fishing pressure

Overexploited



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

11




Closed areas (f)

Closed seasons (f)


B

C F = fq

Output controls (C)




C = FB





M

R

G

Biomass

F=fq

Nt

t

R

t

tage

Wt

t

Ft

tc

C

Statistical

CEDRS

trends assessment

adaptation

Analytical

Experimental

Research

CEDRS

assessment

predictions

f

q

+ sd


Analytical approach



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

12




Effort (numbers)

Length (cm)

Basic research data

Migration (tagging)


Age

Natural Mortality


MMSY =



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

13





Increase in

- Resolution

- Linked data

- Costs








2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

14

Biomass



Recruitment

Growth

Natural mortality


Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

Biomas s

Fishing

Nutrients

Pressure

Driver

State


2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

15


Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Size of fish

B

io

ma

s s

Fishing

Nutrients

Pressure

Driver

State

Fishers Managers


public


Role of science



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

16

Goal



















2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

17


Catch

Effort

Fopt

C = fqB


y = 30xR2 = 082

y = 26 xR2 = 08157

0

5

10

15

20

25

30

35

40

45

50

0 2 4 6 8 10 12 14 16


Cat

ch (

tKm

^2y

ear)

Malombe

Chilwa

MweruChiuta

Albert

Itezhi-tezhi

Edward

Bangweulu

Tanganyika

Nasser amp Kariba

Turkana Kivu

Malawi

Victoria 19702


Volta Kainji



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

18


Systems differ

in productivity



in effort dynamics


Scaled indicators










2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

19



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

20










2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

21






2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

22


Scale of variation

Time Process

decadal community

annual stocks

seasonal year class


1955 1960 1965 1970 1975 1980 1985 1990 1995

Year

0

1

2

3

4

5

6

7

8

x 1000 kgvessel

small




2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

23


Normal pattern


El Nino pattern



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

24


What type of system

stable ndash pulsed


use change




Fish communities


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent


2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

25


a fish community

Size

Biomass


A fish community



Competition

Predation


Piscivores


2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

26



Lake Tanganyika



Lake Mweru



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

27




2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

28



Length (cm)

MolluscInsect


Molluscivore


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850

25

50

75

100

125

150

175

200

1970 - 1972


2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

29

Size

Biomass


levelshellip












2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

30


Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent




Competition

Predation


Piscivores

Fishing pressure


2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

31


Catch

Fishing effort








2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

32

time

N

Population growth










2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

33









2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

34


(population)

SurvivalFecundity












2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

35






Periodic strategist



of small offspring




2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

36


history




trophic position

migratory behaviour



Resilience Low


Life span 24 years

Max length 150 cm


Trophic level 36

Migratory no



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

37




Life span 11 years



Trophic level 44


Periodic


Lake Mweru

Resilience High


Life span 11 years

Max length 40 cm


Trophic level 20

Migratory no



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

38



Resilience High


Life span 25 years

Max length 5 cm



Migratory no









2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

39



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Competition

Predation


Piscivores

Fishing pressure


2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

40


Piscivores


Competition

Predation


Fishing pressure

driving force



Constant systems

Pulsed systems







2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

41



0

20

40

60

80

100

0 1 2 3 4 5 6 7 8


Abu

ndan

ce (

N)



Age at 50 maturity



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

42

Fishing mortality

Age (years)

Inst

anta

neou

s ra

te o

f m

orta

lity

Predation mortality

From ICES (1997)



effort




2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

43






Reduced growth (6)




Small

Random

Large




= genetic changes



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

44



Mortality on



Small

Random

Large


fishing

Age (size)

Abu

ndan

ce (L

og N

)






2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

45


Abu

ndan

ce

Size



phytoplankton

zooplankton

small fish

big fish

Year

1976 1978 1980 1982 1984 1986 1988 1990 1992 1994

Slo

pe

-10

-9

-8

-7

-6

-5





2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

46

Question








2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

47





Kolding et al 2003



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

48

2

3

4

5

Tro

phic

leve

l

Pauly et al (1998)





27 fishing methods

25 kgday

74 species utilized





2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

49






How









2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

50





Fishing pressure




Intercept = Iasd










2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

51



Ecosystems

Fish communities

Fishing techniques


Economics

Administration

Env

ironm

ent



Lake Jaba Nigeria

Trap fishermen

Lake Mweru Zambia


2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

52




2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

53




2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

54











2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

55


number of units

efficiency

Effort (f)


More of the same



=development


Uh


opportunities

0

20

40

60

80

100

120

140

160

180

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fish

erm

en (

1000

)

Cat

ch p

er

fishe

rman

(to

ns)

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

4000000

Qua

ntity

(to

ns)





2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

56









Goal






communities



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

57


indicators







copy Wageningen UR

End hellipbeginning


2112011

58






low low low

high high low

high low high















Environment


Life history traits



2112011

58






low low low

high high low

high low high















Environment


Life history traits


an ecosystem approach to fisheries...

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