A review of the methods used to estimate, reduce, and manage bycatch mortality of pacific halibut in the commercial longline groundfish fisheries of the Northeast Pacific

Management of the hook-and-line-only fishery for Pacific halibut Hippoglossus stenolepis in waters off the United States and Canada requires discard to the sea of Pacific halibut bycatch (Out of season. undersized. or by fishermen without individual quotas or licenses). Depending oil hook type and release methods, Survival from longline discards can vary from nearly 100% to none. Conversion in the early 1980s from J-hooks, used by foreign fleets and the domestic halibut fleet, to circle hooks, now used by most domestic longline fishermen. increased survival potential through less damaging hooking locations. Bycatch mortality caused by a fishery was estimated by applying a discard mortality rate to the total halibut discarded. On-board observers collected viability data used to calculate annual fishery-specific Pacific halibut discard mortality rates and collected fishery-specific bycatch rate data used to estimate total bycatch. Limits on bycatch mortality. which closed fisheries when exceeded, provided an incentive for the longline fleet to practice careful release. Estimated halibut bycatch mortality dropped following careful release regulations. Results of tagging Studies on halibut released using careful release demonstrated that the distribution of hook injuries shifted to minor and moderate injuries compared with moderate and severe injuries when careful release did not occur. Tag return rates used to quantify Survival by injury type led to criteria describing the injuries.