Shark bycatch in the Japanese high seas squid driftnet fishery in the North Pacific Ocean

From the late 1970s to 1992, large-scale pelagic driftnet fisheries in the North Pacific targeted flying squid (Ommastrephes bartami), tunas and billf ishes. In the late 1980s, cooperative multinational scientific observer pro grams began on Japanese, South Korean, and Taiwanese driftnet fleets fishin g in international waters. These programs resulted in some of the most comp rehensive data on the distribution and abundance of epipelagic species in t he Noah Pacific transition region. Eleven elasmobranch taxa were sighted by observers in the Japanese flying squid driftnet fishery. Blue sharks accou nted for 93.7% of the elasmobranch bycatch in 1990 and 1991. In 1991, obser vers collected biological data on a limited number of shark and fish specie s, including blue shark (Prionace glauca) and salmon shark (Lamna ditropis) . Canada experimented with a flying squid driftnet fishery in coastal water s near British Columbia beginning in 1979 but it was terminated in 1987 bec ause of unacceptable levels of bycatch. Blue shark and salmon shark CPUEs w ere an order of magnitude higher in the coastal Canadian experimental drift net fishery than in the high seas squid driftnet fishery. The average size of blue sharks in coastal catches was larger than sharks caught in the high seas fishery. The seasonal pattern of CPUE in the Japanese squid driftnet fishery was consistent with the seasonal location of the fleet and the subt ropical-subarctic ecological gradient that polarizes salmon and blue sharks . Errors-in-variables regression equations are provided to convert among to tal length, eye-fork length, and precaudal length measurements. Crown copyr ight (C) 1998 Published by Elsevier Science B.V. All rights reserved.