Stock Assessment Stock Assessment Methodologies for Reef Methodologies for Reef

Systems: A Joint AnalysesSystems: A Joint Analyses

Gerard DiNardoNOAA Fisheries, Pacific Islands Fisheries

Science Center, USAQin Chuanxin

CAFS, South China Sea Fishery Research Institute, China

Hui-Hua LeeJoint Institute for Marine and Atmospheric Research, University of Hawaii, USA

GoalGoal• Capacity Building via Staff Exchange

– Dr. Qin to PIFSC for 30 days to learn about reef stock assessments

– Time permitting, conduct preliminary stock assessments of key species in the Guangdong Province based on available data

• But

– Data sets are large and not easily accessible (still raw)

– Habitat and stock enhancement occurring

– Have to understand the extent and associated benefits of enhancement programs before conducting any assessment

Work PlanWork PlanDay 1-15•Data screening, rectification and mining•Spatiotemporal views of the data•Exploratory analyses and literature search

Day 16-30•Identify analytical strategy (right tool for the job) •Conduct preliminary analyses •Initiate development of an Assessment strategy allowing for ecossystem enhancements

Stock Assessment ProcessStock Assessment Process

Population ModelPopulation Model

CatchCatchLogbooks,Logbooks,Observers,Observers,

Age/Size DataAge/Size Data

AbundanceAbundanceResource Survey,Resource Survey,

Fishery CPUE,Fishery CPUE,Age/Size DataAge/Size Data

BiologyBiologyAge,Age,

Growth,Growth,MaturityMaturity

Advanced ModelAdvanced ModelHabitat,Habitat,Climate,Climate,

EcosystemEcosystem

Stock StatusStock Status

Conceptual population assessment model for the annual change in biomass (B) of a harvested

LMR

• Biomass additions in year T due to:– Somatic growth (G)– Recruitment (R)

• Biomass losses in year T due to:– Fishery yield (Y)– Natural deaths (D)

1T T T T T TB B G R Y D

Adapted from Russell (1931. Some theoretical considerations

on the “Overfishing” problem. Journal du Conseil, 6:1-20)

Equilibrium, Sustainability, and Maximization• An equilibrium stock

size has an associated sustainable equilibrium yield

• Maximum sustainable yield (MSY) generally occurs at an intermediate stock size and depends on the harvest pattern

• “MSY is the largest average yield that can continuously be taken from a stock under existing environmental conditions” ~ Ricker

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 2 4 6 8 10 12 14 16 18 20

1964

2001

MaximumSustainable Yield(MSY)

Catch > Equilibrium Reduces Biomass

Catch < EquilibriumAllows Growth

EquilibriumYieldCurve

STOCK BIOMASS K

CA

TC

H

Biological Reference Points• Reference points measure the status of a fish stock to

provide rational guidance for management– Limit reference points express the maximum degree of safe

exploitation

– Target reference points express the degree of exploitation desire by management

• MSY is the limit for USA marine fisheries and optimum yield is the target

• The target optimum yield is MSY “as reduced by any relevant economic, social, or ecological factor”

~ Sustainable Fisheries Act (2008)

Effects of an Environmental Shift

Favorable Environment

UnfavorableEnvironment

Conceptual model for artificial reef enhancement: Substitute habitat for environment

MSY

9

Incorporating Environmental Signals into Forecasts of Future Recruitment and Catch

Requirements for Advancing Requirements for Advancing AssessmentAssessment

(Data Needs) (Data Needs) • Catch Monitoring Catch Monitoring • CPUE Time Series CPUE Time Series • Size Structure Size Structure • Movement (connectivity) Movement (connectivity) • Stocking numbersStocking numbers

Explore utility of size-based assessment approach (life history Explore utility of size-based assessment approach (life history information and length data): PIFSC-SEFSC-UM Joint information and length data): PIFSC-SEFSC-UM Joint Collaboration Collaboration

Thank You