Observer-reported skate bycatch in the commercial groundfish fisheries of Alaska

摘要

We analyzed skate catch data collected by observers in theudNorth Pacific Groundfish Observer Program (NPGOP) from 1998 through 2008 to document recent changes in the identification of skates by observers and to examine the species composition of observed skate catch in Alaska’s groundfish fisheries as well as recent trends in skate retention by commercial fishermen. Historically, almost all skate bycatch has been reported by NPGOP observers asud“skate unidentified.” However, since 2004 observers have been trained to identify skates to the genus and speciesudlevel. In 2008 over 95% of all skates were identified at least to the genus level, and over 50% were identifiedudto species. The most common species of skates identified by observers in groundfish fisheries are Bathyraja parmifera (Alaska skate), Raja binoculata (big skate), and Bathyrajaudaleutica (Aleutian skate). Species composition of reported skate catch generally reflects recent survey-derivedudbiomass estimates, with B. parmifera dominating the catches in the Bering Sea and, to a lesser extent, in the Aleutian Islands region, and species of the genus Raja dominating catches in the Gulf of Alaska. A relatively high percentage of the skate catch on longline vessels is still reportedudat the family or genus level because of difficulties in the identification of skates not brought onboard the vessel. For the larger skate species, the proportion retained for processing has increased in recent years as the market price for skate product has increased. Although observed skate catch does not give a complete account of skate bycatch in the fisheries of the region, observer data provide critical information for the appropriate management of skate populations inudAlaska.