Evaluation of Modified Crab Pots to Increase Catch of Pacific Cod and Decrease Bycatch of Pacific Halibut

Abstract

Use of crab pots to catch Pacific cod Gadus macrocephalus has increased in the Gulf of Alaska and Bering Sea. We evaluated a variety of crab pot modifications that we hoped would increase the catch of Pacific cod and decrease the bycatch of Pacific halibut Hippoglossus stenolepis. During September and October 1990, seven types of modified crab pots and one type of unmodified crab pot were fished during a 26-d period. Pot modifications included one-way fish retention devices (FRDs) and reductions in the size of tunnel-eye openings. Pots with FRDs had significantly higher (P = 0.0001) catches of Pacific cod than pots without FRDs and tended to have the lowest bycatches of Pacific halibut. Pot tunnel-eye opening dimensions of 20.3 × 17.8 cm significantly (P = 0.0001) reduced bycatch of Pacific halibut without significantly reducing the catch of Pacific cod. More than 90% of the Pacific halibut in all treatments were judged to be in “excellent” condition. Pacific halibut bycatch rates for pots with FRDs varied from 26.5 to 57.1 kg of Pacific halibut per metric ton of Pacific cod.