Accounting for Bycatch in Management of the Pacific Halibut Fishery

Abstract

Since the 1960s, fisheries for groundfish other than Pacific halibut Hippoglossus stenolepis have caused an average of about 9,000 metric tons (mt, round weight) of halibut bycatch mortality every year, whereas annual directed catches of Pacific halibut have varied from 13,000 to almost 50,000 mt. About half of the bycatch consists of juvenile Pacific halibut caught in Alaska, some of which would otherwise migrate south and contribute to the fishery in British Columbia. These interceptions have long been a difficult issue for the United States and Canada. At recent levels of high juvenile abundance, the juvenile bycatch reduces coastwide recruitment by about 10%. The resulting yield loss, plus bycatch of adult fish, reduces yield to the directed fishery by about 11,000 mt per year. Migration modeling indicates that the yield loss due to bycatch occurs almost entirely in the area where the bycatch is taken. In particular, bycatch in Alaska reduces Pacific halibut yields in British Columbia by, at most, a few percent. During the 1980s and early 1990s, annual quotas in the directed Pacific halibut fishery were reduced by an amount equal to, or sometimes greater than, the total Pacific halibut bycatch mortality, and the quota reduction was distributed among regulatory areas in proportion to Pacific halibut exploitable biomass. At present, the Pacific halibut quota in each regulatory area is reduced by the amount of adult Pacific halibut bycatch mortality in that area, and the target exploitation rate is adjusted downward (slightly) to offset the bycatch mortality of juveniles.