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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