Data Collection and Stock Assessments: Role of Science

Marine Fisheries 101 Workshop

April 24, 2018

Florida Fish and Wildlife Conservation Commission

Fisheries Science: Concept of a Unit Stock

▪ Unit Stock – fundamental concept

▪ We can not practically account for fish that

move into and out of a population

▪ Need to define a stock such that emigration

from and immigration to the population are

assumed to be negligible

▪ Defining the unit stock allows us to focus on

rates of growth and mortality within the

population

▪ Unit stock defined by genetic similarities

▪ Snook, red drum –Atlantic and Gulf Coast stocks

▪ Yellowtail Snapper – single stock in Florida

Unit Stock

X

Marine Fish Life History Strategies

▪ Most fish produce many more young than will

survive to adulthood

▪ Mortality during first few weeks of life > 95%

▪ Larval and juvenile fish protect themselves from

predators

▪ Getting to nursery habitats as quickly as

possible

▪ Being inconspicuous

▪ A large number of Florida’s marine fish

dependent on inshore habitats even if adults

reside primarily offshoreTarpon LarvaSource: Bonefish Tarpon Trust

Juvenile Gag Grouper Caught on Inshore Seagrass Bed

Not all Mothers are Equal

212 17-inch femalesOne 24-inch female

produces as many eggs as…

0

50

100

150

200

250

Le

ngth

(cm

)

0 5 10 15 20 25 30 35 40 45 50

Age (years)

Differences in Growth Rate by Species

Dolphin Red Drum Gag Grouper Snook Red Snapper

Marine Fish Life History Variation

Mature in 4-5 months Max Age = 5 years

Mostly found offshore, Do not aggregate

Spawn multiple times per year

Dolphin

Mature in 2 years Max Age = 50 years

Offshore as adults, juveniles reside inshore but generally not in

estuaries

Do not aggregate to spawn, spawn multiple times per year

Red Snapper

Mature in 1-7 years Max Age = 20 years

Mostly inshore throughout life, young in mangroves

Begin life as male, some change to female between age 1-7

Aggregate to spawn; some skip years

Common Snook

Mature in 8 years Max Age = 25 years

Juveniles inshore for 3-4 mo. then

offshore

Begin life as female, some change to

male at age 10-11

Aggregate to spawn

Gag Grouper

Mature in 3-4 years Max Age = 50+

years

Inshore until age 3-4, then offshore

Aggregate to spawn near passes

Red Drum

Fisheries Stock Assessments

▪ Basic purpose is to reconstruct the history of a stock up to the

present day to determine:

▪ If a stock is capable of replacing losses due to natural and

fishing related mortality

▪ If unusual events have occurred that impact the stock condition

▪ Poor recruitment during certain years

▪ High mortality on certain age classes

▪ Environmental events such as red tides or cold kills

▪ More complex models calculate age-specific mortality and

require information on the distribution of ages in the population

(otoliths)

▪ Includes data from the fishery and independent scientific surveys

in conjunction with species-specific life history data

Snook Otolith

Why is age and reproductive data so important?

▪ Stock assessment models essentially reconstruct the past

▪ Fisheries often have variability in recruitment year-to-year

▪ If we have enough unbiased age samples we can determine:

▪ Year and age specific mortality

▪ Relatively good recruitment years versus poorer ones

▪ If environmental events and/or fishing are resulting in

selective mortality on certain age classes

▪ Reproductive data on age at first maturity and fecundity

▪ Age at first maturity can change within a population and

earlier maturation often a sign of stress

▪ Fecundity changes with age, size and in some cases

environmental conditions – these factors need to be

figured into assessments

Highly Magnified Image of Gag Grouper Ovary

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29F 20040

12

3

Sp

aw

nin

g b

iom

ass

Age (yr)

F 2004 F goal F = 0

F

Commercial Fisheries

Monitoring

Scientific Surveys

RecreationalFisheries

Monitoring

Biology and Life History Research

Stock Assessment – Data Integration

Types of Fisheries Data

▪ Fishery-Dependent: derived directly from

the fisheries:

▪ Commercial

▪ Private Recreational

▪ For-Hire

▪ Fishery-Independent: collected directly by

scientists, i.e., derived from activities that

do not involve the commercial or

recreational fisheries

Commercial Fisheries Data Collection

▪ Marine Trip Ticket program -- census

▪ 1,200 licensed commercial dealers

▪ 15,000 licensed commercial fishers

▪ ~300,000 trip tickets submitted annually

▪ Sub-sampled for species id, lengths, weight,

sex, age

Recreational Fisheries Data Collection

▪ MRIP conducted by FWC with NOAA-NMFS funding and

coordination – survey

▪ 7.2 million marine anglers fishing in Florida

▪ 20 million fishing trips annually

▪ ~ 30,000 angler interviews conducted annually

▪ Bimonthly mail survey to estimate effort

▪ Sub-sampled for species id, lengths, weight, age

▪ Gulf Reef Fish Survey (GRFS) provides more timely and precise data for

reef fishes harvested from the Gulf

▪ Additional angler interviews at offshore access points

▪ Targeted mail survey

▪ Funded through June 2020 (oil spill restoration $)

▪ Spiny lobster mail survey – following mini-season

▪ For-hire at sea discard monitoring

▪ Snook carcass drop-off at tackle shops

▪ Atlantic coast red snapper targeted survey

▪ Include App for angler reporting (iAngler)

Recreational Data Collection: Florida Enhancements

Northern Indian

River Lagoon

Southern Indian

River Lagoon

Florida Keys

Charlotte Harbor

Tampa Bay

Cedar Key

Apalachicola

St. Johns River

FWC Juvenile Monitoring Program

▪ Over 600 estuarine

sites sampled monthly

▪ ~7,500 sites sampled

annually

Limits of Assessments: How research data can be used

to inform management in between assessments

Tampa Bay

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

0.0

2.0

4.0

6.0

8.0

Charlotte Harbor

Year

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Northern Indian River Lagoon

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

Catc

h-p

er-

un

it-e

ffo

rt(n

um

ber

of

sn

oo

k p

er

hau

l)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Southern Indian River Lagoon

Year

1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

2016

Catc

h-p

er-

un

it-e

ffo

rt(n

um

ber

of

sn

oo

k p

er

hau

l)

0.0

2.0

4.0

6.0

8.0

Ca

tch

pe

r U

nit

of

Eff

ort

(N

o. o

f F

ish

/N

et

Ha

ul)

Biology and Life History Studies

▪ Tagging studies

▪ Fish movement, behavior, and

connectivity

▪ Fish age and growth

▪ Reproduction

▪ Feeding habits

▪ Release mortality

Spawning Potential Ratio (SPR)

SPR

Target

Limit or

Threshold

0%

20%

40%

60%

80%

100%

Unfished Condition

Fished

SPR = Spawning Biomass Fished

Spawning Biomass Unfished

Example at left:

SPR = 40%

South

East

Data

Assessment

Review

SEDAR – Federal Stock Assessment Process

▪ Involves 3 workshops:

▪ Data Workshop

▪ Assessment Workshop

▪ Review Workshop

▪ FWC deeply involved in all stages:

▪ Provides data

▪ Leads or assists with analyses

▪ Integrated in the review process