Prediction of bycatch mortality based on reflex impairment during the commercial snow crab (Chionoecetes opilio) fishery

The mortality of the non-retained crab during a commercial crab fishery in the eastern Bering Sea must be included as part of the total catch removal calculations used to calculate harvest levels. Best available information estimates the crab bycatch mortality to be 50% in pot fisheries but it is widely acknowledged that further refinement of this estimate is needed. To accomplish that goal, the Reflex Action Mortality Predictor (RAMP) method was applied to snow crab discarded during the 2010 commercial fishing season. The RAMP method evaluates the responses of the crab to a set of six reflexes. Studies have shown reflex responses accurately predict mortality in 91% of these crabs. Biologists were placed on board commercial fishing vessels where they assessed sublegal males and female snow crab just prior to discard. The amount of crab reflex impairment was appeared to be influenced more by temperature and wind than by sorting practices. Preliminary results from vessels which had efficient sorting practices showed that over 90% of all crab discarded showed no reflex impairment during relatively mild weather conditions. This study is a first step in improving the bycatch mortality estimate needed to calculate crab harvest levels in the eastern Bering Sea.