centre for shellfish research shellfish culture and nature conservation aad smaal institute for...
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![Page 1: Centre for Shellfish Research SHELLFISH CULTURE AND NATURE CONSERVATION Aad Smaal Institute for Marine Resources and Ecosystem Studies Yerseke, NL](https://reader036.vdocuments.site/reader036/viewer/2022062519/56649cd65503460f9499d161/html5/thumbnails/1.jpg)
Centre for
Shellfish Research
SHELLFISH CULTURE AND
NATURE CONSERVATION
Aad Smaal
Institute for Marine Resources and Ecosystem Studies
Yerseke, NL
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Centre for
Shellfish Research
Delta
North Sea
IMARES: NEW INSTITUTE
Former Fishery Institute merged
with 2 other groups
ENVIRONMENT
FISHERY
AQUACULTURE
Shellfish Research, Yerseke
- population dynamics
- carrying capacity
- culture innovation
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Centre for
Shellfish Research
PROBLEMS IN CULTURE AND CONSERVATION
• Shellfish culture / fisheries always has an impact on the
ecosystem
• Shellfish culture occurs often in areas that are now
protected for nature conservation
• What are the impacts, positive / negative, acceptable ?
• Source of conflicts between stakeholders
• Role of science / politics / governments
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Centre for
Shellfish Research
OUTLINE
• ROLE OF SHELLFISH IN THE SYSTEM
• IMPACTS OF CULTURE
• REGULATION
• STAKEHOLDERS
• CONSERVATION and EXPLOITATION
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Centre for
Shellfish Research
Food
Habitat Feedbacks
ROLE OF SHELLFISH
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Oosterschelde case: storm surge barrier
Analysis of the role of mussels in the ecosystem:
benthic tunnels, mesocosms, models
• Residence time >• Water transparency >• Nutrient loads <
• Internal nutrient cycles more important• Adaptation of phytoplankton• Maintenance of primary production
Prins & Smaal, 1994; Prins et al, 1998; Smaal et al, 2001
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Nutrient (N) regeneration through direct excretion + biodeposit mineralization up to 40 % of total N regeneration
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Through grazing increase in phyto plankton turnover ; optimal mussel growth at intermediate biomass
Bottom-up control at low mussel density and top-down control at high mussel density
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Centre for
Shellfish Research
FUNCTIONAL ROLE:
• Grazing of phytoplankton
• Production of biodeposits
• Regeneration of nutrients
• Promotion of algal growth
• Stabilization of the ecosystem
feedbacks through filter feeding
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Centre for
Shellfish Research
FOOD FOR BIRDS:
• shellfish beds are essential as food source for waders and diving ducks
• shellfish stocks may show large variability in time
• birds may switch prey
• collapse of both mussel and cockle stocks caused problems in Wadden Sea and Wash in ’90
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0
50
100
150
200
250
mln kg fresh
1971 1974 1977 1980 1983 1986 1989 1992 1995 1998
0
1
2
3
4
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000
bestand droog
Mussel stock(index)
Eider duck mortality
1991
Cockle
stock
Call for shellfishery policy
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0
100
200
300
400
500
mln kg fresh
1990 1992 1994 1996 1998 2000 2002
BSF dynamics
mussel
macoma
cockle
0
50000
100000
150000
200000
250000
300000
350000
75767778798081828384858687888990919293949596979899000102
Oystercatcher decrease after
low shellfish stocks 1996 due
to severe winter
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Centre for
Shellfish Research
CONCLUSION FOOD
FOR BIRDS
• Shellfish is major resource
• Minimum stock required for longterm maintenance of
bird populations
• high shellfish dynamics sometimes don’t match bird needs
• call for protective measures
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0
20
40
60
80
100
120
140
160
180
51 55 59 63 67 71 75 79 83 87 91 95 99
mln kg fresh
Import
Wad
Delta
0
20000
40000
60000
80000
100000
77 80 83 86 89 92 95 98
MILJOEN KG VERS
vd
ws
os
wad
HARVEST IN NL FROM
CULTURE AND FISHERY
MUSSEL: 100 MLN KG
COCKLE: 20 MLN KG
OYSTER: 3 MLN KG
00.5
11.5
22.5
3
mln kg
52 57 62 67 72 77 82 87 92 97
oyster production
Crassostrea
Ostrea
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ROLE AS HABITAT
Biocoenose (Mobius, 1880)
Epibenthic shellfish beds form structures
nr of species > 150 (Sayer, 2002)
Biodiversity higher in sublitoral (Buchsbaum & Sayer, 2003)
Impact of culture ?
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Centre for
Shellfish Research
IMPACTS OF SHELLFISH CULTURE
Feedbacks
impact on Stocks
Food
Habitat direct:
bottom culture – infauna (clams, cockles)
- epifauna (mussels, oysters)
indirect: suspended culture
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WILD LITORAL STOCK
WILD SUBLITORAL STOCK
CULTURE PLOTS
SHELLFISH FLOW
natural spatfal natural spatfal
Seed fishery
harvest
RESULT: NET INCREASE OF BIOMASS
IMPACTS on STOCKS
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IMPACTS on STOCKS
Case study : Wadden Sea bottom culture
Model calculation wild beds vs culture plots:
Musselseed plots/wild - Growth 1.7 x higher
- Density 0.6 - Mortality 0.8
Net result: stock – harvest 1.15: 15 % more biomass
Note: Carrying capacity problems due to overstocking
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IMPACTS on HABITAT
Bottom culture:
• Culture of mussels and oysters
on bottom plots,
frequent fishery activities
effects on biodiversity depend on
local conditions
• Culture / fishery of infauna :
sediment change ?
mortality of bycatch ?
less spatfal ?
many studies
controversial issue
ban on cockle fishery Waddensea 2003
Wild
bed
Cultureplots
muddy sub
(Von Westphalen, 2005)
sand
(van Gils et al, 2004)
Impact of cockle fishery
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Seed fishery on wild beds
Mussels : focus on unstable beds
Littoral : experimental seed fishery
to test impact on stability:
no net effect of fishery on seed mussel density
Sublittoral : research topic
Major issue in actual discussion in NL
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IMPACTS on HABITAT
Suspended culture:
• Sediment deposition
depomod application
mostly for fish farming
useful for shellfish
(no external input, only concentrating material)
• Benthic community
various studies: (Grant et al, 2005; DEPOMOD)
- local scale effects
- depend on hydrodynamics, site etc
- can both enhance or reduce species nr
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Centre for
Shellfish Research
SUMMARY OF IMPACTS
Stocks: AVERAGE INCREASE
Habitats: bottom culture / seed fishery
epifauna BIODIVERSITY
HABITAT COMPLEXITY
infauna SEDIMENT/BENTHOS
suspended culture SEDIMENT/BENTHOS
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POLICY & REGULATION
NATIONAL: policy document 2004
“Space for harvest”
- sustainable use
- innovation by industry, less impacts
- closed areas
EU: Bird and Habitat Directive (implementation NL 2004)
- For nature conservation areas
- in many cases shellfish culture areas
- permit required for each seed fishery period (2x p yr)
- industry has to perform an appropriate assessment
of possible impacts on management objectives
- permits can be stopped by court after objections
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STAKEHOLDERS
INDUSTRY RESPONSE
• triple P approach : Profit, Planet, People
= continuous improvement
= planning + evaluation + research
= draws up fishing plans,
= uses black boxes onboard fishing vessels
= register activities in an electronic logbook
• Develop an innovation agenda
• Stakeholder involvement
• Setting up research: innovation
continuous improvement
ProfitProfit
PlanetPlanetPeoplePeople
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INNOVATION: life cycle control
PRODUCT
HATCHERY
SEED
COLLECTORS WILD SEED
FISHERY
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IMOZA - Doove Balg
IMOZA - Verversgat
IMOZA - Vlieter
IMOZA - Stompe
IMOZA - Malzwin
IMOZA - Bollen
Wietex - Texelstroom
Wietex - Oergat
Wietex - MalzwinPD - Malzwin
West 6 - Malzwin
Zaadinvang locaties
Kustlijn
Laagwaterlijn
Naam: Produs 1c
Auteur: J.M.D.D. Baars
Archief: q:/projects/kleine_opdr/pk05 Datum:juli 2005
Centrum voor Schelpdier Onderzoek
NederlandsInstituut voor
Visserijonderzoek
MUSSEL SEED HATCHERY/
COLLECTORS NURSERY
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STAKEHOLDERS
NGO RESPONSE
• objected against seed fishery permits
• case in court in spring and autumn
• court decision: fishery could go on
BACKGROUND
Nature conservation areas should not be exploited
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Editorial in PloS Biology of Nov 14, 2006 based on
culture
conservation restoration
X
?
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NATURE CONSERVATION STRATEGIES
• Protection against adverse impacts
• Conservation of non-impacted areas
• Prevention of new impacts
• Habitat restoration
• Habitat creation
• Multi-functional use
• Sustainable use
exclusion
mitigation
integration
Dynamic / control
Static / spontaneous
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NATURE CONSERVATION = CULTURAL ISSUE
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PARADOX OF EXTENSIVE EXPLOITATION
• extensive exploitation is part of nature and contributes to
ecosystem processes (food, feedback, habitat)
• exploitation depends on natural dynamics and farmers
want to become less dependent
• nature conservationists want to restrict exploitation
• 2 forces in the direction of intensification
• more intensive culture in existing areas calls for more
criticism
• loss of extensive culture
• future need for shellfish restoration
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Centre for
Shellfish Research
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