2018 Benchmark Stock Assessment of Main Hawaiian Islands Kona Crab

This benchmark assessment improved upon filtering of data records by re-defining fishing effort as a single reported fishing day and exploring fisher effects (individual fisher effects and cumulative fishing experience) in catch-per-unit effort (CPUE) standardization. Additionally, this 2018 assessment addressed uncertainty previously unaccounted for, including unreported catch, incidental mortality of female crab catch following the prohibition of female crab harvest in 2006, and a Bayesian prior on the initial ratio of biomass to carrying capacity. The assessment used a state-space Bayesian surplus production model in a new user-friendly framework, Just Another Bayesian Biomass Assessment (JABBA). The model fit standardized CPUE data in a generalized Pella-Tomlinson surplus production model. Parameter distributions were estimated in a Bayesian framework, which estimates parameter posterior distributions starting from prior distributions and fitted to data. Annual harvest rates (H), harvest rate at maximum sustainable yield (H_MSY), annual biomass (B), and biomass at maximum sustainable yield (B_MSY) were estimated in JABBA, among other outputs. Results from this assessment conclude that in 2016, the Hawaii Kona crab fishery was not overfished (defined as B/B_MSY < 0.7) with a 0.01% probability of the status being overfished in 2016. In 2016, the stock was not experiencing overfishing (defined as H/H_MSY > 1), with 0% probability of overfishing occurring. The model converged and a retrospective analysis detected no strong retrospective pattern. Projections from 2020 to 2026 quantified overfishing risks for various future catch levels, and concluded that a 50% risk of overfishing in 2026 corresponds to an annual reported catch of 33,989 lb.

Kapur MR, Fitchett MD, Yau AJ, Carvalho F. 2019. 2018 Benchmark stock assessment of main Hawaiian Islands Kona crab. (NOAA Tech Memo NMFS-PIFSC-77).