Indian Ocean yellowfin tuna close-kin markrecapture design study

Close-Kin Mark-Recapture (CKMR) is a genetics-based method for estimating key population
metrics useful for independent assessment of stock status, or as data inputs for integrated stock
assessment models, or as inputs to management procedures. This report evaluates a range of
sampling scenarios for Indian Ocean yellowfin tuna to provide estimates of Total Reproductive
Output (TRO, similar to spawning stock biomass), depletion in TRO, adult mortality and mean
recruitment. This design study evaluates the sample sizes of juveniles and adults required to give
precise estimates of these population metrics.
The analysis used a simplified population model that reproduced recent yellowfin tuna population
dynamics, but in an equilibrium framework. Under these conditions, annual sampling levels of
25,000 to 30,000 samples were predicted to yield useful insights on population metrics with
reasonable precision in the estimates. Specifically, the depletion in total reproductive output
(TRO), could be estimated with a coefficient of variation (CV) of 15% with 30,000 annual samples
over 5 years. After the initial 5 years are complete, a CKMR monitoring program would build on
the existing data set to provide ongoing information for assessment and management.