Investigating Trawl Gear Modifications to Reduce Mortality of Bering Sea Crab Fisheries

• Activity Number: 456
• Type: Topic Contributed
• Date/Time: Wednesday, August 4, 2010 : 8:30 AM to 10:20 AM
• Sponsor: Section on Statistics and the Environment
• Author(s): Loveday L. Conquest*+ and Carwyn Hammond and Craig Rose
• Companies: University of Washington and National Marine Fisheries Service and National Marine Fisheries Service
• Keywords: crab mortality ; Bering Sea fisheries ; fisheries management ; generalized linear models

Abstract

Management of Bering Sea crab fisheries must account for unobserved mortality of crabs that encounter bottom trawls, but are not captured. An approach to predict delayed mortality of injured crabs is the Reflex Action Mortality Predictor (RAMP), which establishes a relationship between reflex impairments and mortality. RAMP curves from a 2007 study were updated with additional data collected in 2008. RAMP curves were used to predict unobserved mortality from reflex scores for Bering Sea Tanner crab and Snow crab, following encounters with different parts of bottom trawl gear (footrope, sweep and alternative types of these two geartypes). Using generalized linear models, we also investigated whether the alternative footrope and sweep designs would reduce the predicted mortality rates of crab. The alternative gear types did reduce mortality, by different amounts depending upon species.