Predicting Discard Mortality for Snow and Tanner Crab in the Alaskan Bottom Trawl Fishery: Can It be Done?

The fate of incidentally captured snow crab (Chionecetes opilio) and Tanner crab (C. bairdi) in Alaskan groundfish bottom trawl fisheries is not expressly understood. The uncertainty in predicting fatality restricts assessments of the crab populations and depiction of trawl fleet impacts. To predict the fate of discarded crab we used an adapted reflex action mortality predictor, which uses the absence of several reflexes to predict delayed mortality. Crabs caught in the trawl were assessed using this predictor, then samples with the different reflex states were observed over time and mortality was noted. Previous research evaluated the potential to use this method to predict delayed mortality of crabs that interact with the gear, but are not captured. This study aims to validate the use of this prediction method on captured crabs, to compare its application to crabs that encounter the trawl but are not landed to those that are, and to evaluate the influence of variables such as haul time, time on deck, and catch volume.

This project is being conducted as part of the Collaborative Fisheries Research Graduate Fellowship Program, which provides opportunities for scientists to conduct research jointly with fishermen, combining the unique knowledge and experience of each to enhance research. This work will benefit from the support of the Program community as well as from previously developed partnerships in Alaska.