Accounting for bycatch in management of the Pacific halibut fishery

by William G. Clark  ^and Steven R. Hare

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Manuscript accepted (March 98) for publication the North American Journal of Fisheries Management
 

Abstract

 Since the 1960s, fisheries for other species of groundfish have caused an average of about 9,000 metric tons (mt) of Pacific halibut Hippoglossus stenolepis bycatch mortality every year, while directed catches have varied from 13,000 to almost 50,000 mt (both measured in round weight). Around half of the bycatch consists of juvenile fish caught in Alaska, some of whom 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 high levels of juvenile abundance, 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 amount of total Pacific halibut bycatch mortality, and the quota reduction was distributed among regulatory areas in proportion to Pacific halibut 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.
   

Copyright © Steven R. Hare