Bycatch of crab occurs in directed crab pot fisheries as well as groundfish and scallop fisheries. In the crab fisheries, crab bycatch includes females of target species, sublegal (small) males of target species, and non-target crab. In all other fisheries, crabs are a prohibited species, and must be discarded, so every crab caught incidentally is considered bycatch. Crabs caught as bycatch in trawl fisheries are thought to have a high mortality rate (estimated at 80%); in the scallop dredge and pot fisheries for crab and groundfish, mortality is considered to be much lower (between 20 and 50%).
Limits on the bycatch of prohibited crab species have been established in some Bering Sea fisheries, to reduce the impacts on these species traditionally harvested by other gear types. When bycatch limits are reached, fisheries responsible for the bycatch are closed for the rest of the season, or are prohibited from fishing in areas with historically high bycatch rates. Area closures have also been implemented throughout the Bering Sea and GOA to protect crab. In addition to these tools, gear restrictions and other regulations have been implemented to reduce crab bycatch. For example:
- Biodegradable panels are required for pot gear, to minimize bycatch associated with so-called ghost fishing of lost gear.
- Tunnel openings for pot gear are limited in size to reduce incidental catch of halibut and crabs.
- Gillnets for groundfish have been prohibited to prevent ghost fishing and bycatch of non-target species.
- In 1999, the use of bottom trawl gear was prohibited for vessels targeting pollock in the Bering Sea, to reduce crab and halibut bycatch.
In 2011, a trawl sweep modification requirement was implemented for vessels participating in the Bering Sea flatfish fishery, to raise the trawl sweep off the seafloor. Research has demonstrated that this gear modification reduces unobserved mortality of red king crab, Tanner crab, and snow crab. The Council intends for a similar modification to be implemented in the Gulf of Alaska.