Catch abilities of bottom-set longlines and losses from killer whales for the halibut fishery in the Okhotsk Sea
Data on species and size structure of catches, productivity and losses of catching are obtained in the experiment on the pacific black halibut (Reinhardtius hippoglossoides) fishery with bottom-set longlines conducted aboard RV Saburovo at the coast of West Kamchatka in March-April 2004. Economic losses from killer whales are determined, as well. Generally, the halibut, Lycodes, and Bathyraja made about 90 % of the catches, but the species composition changed with the depth: on 200-300 m pacific cod Gadus macrocephalus prevailed (up tо 60 %) and the portions of Cottidae and Hippoglossus stenolepis were up to 10 %; on 400-500 m the portions of halibut and Lycodes were 30-35 % and the portions of cod and Bathyraja - 10-15 %; on 600-700 m halibut prevailed (more than 40 %), the portion of Lycodes was 20-40 %, and Bathyraja - 15-30 %. Mean effectiveness of the fishing was 17 %, and average CPUE - 21 specimens per cartridge. On the average, every twelfth hook on the depth 600-700 m was with halibut, and every fifteenth hook on the depth 200-300 m - with cod. The total economic losses for the period of experiment were estimated in 89,000 USD (43 % of a vessel income), including 40,000 USD (19 % of the income) caused by attacks of killer whales. Each attack of killer whales brought the losses 6300-6600 USD. Possible ways to decrease these losses are discussed.