Utilizing reflex impairment to assess the role of discard mortality in “Size, Sex, and Season” management for Oregon Dungeness crab (Cancer magister) fisheries

Abstract

We found that crab discarded from Oregon (USA) commercial and recreational fisheries for Dungeness crab (Cancer magister) have lower postrelease mortality than previously estimated. This aligns with the goals of the “3-S” management strategy currently employed for these fisheries, to protect discarded sublegal male (Size), female (Sex), and soft-shell (Season) crab. We found that for the commercial ocean Dungeness fishery, overall discard mortality rates (5 days after release) were 0.080 (95% confidence interval: 0.061–0.100) for females; 0.012 (95% confidence interval: 0.002–0.022) for hard-shell males; and 0.092 (95% confidence interval: 0.026–0.157) for soft-shell males. The overall discard mortality rate for the recreational bay fishery (from a boat) was estimated to be 0.009 (95% confidence interval: 0–0.018). A reflex action mortality predictor relationship, which relates reflex impairment to mortality probability, was created and utilized to estimate mortality rates. Our study highlights the importance of looking not only at discard and mortality rates to evaluate 3-S fishery management, but also the mortality- and bycatch-per-retained ratios and temporal trends relative to changes in effort, animal condition, and catch composition.