Pacific Halibut Bycatch in the Washington, Oregon, and California Groundfish and Shrimp Trawl Fisheries

Abstract

Pacific halibut Hippoglossus stenolepis bycatch rates (catch in numbers or weight per trawling hour) in the Washington, Oregon, and California bottom trawl fisheries were estimated by using observer data collected between 1985 and 1990. Pacific halibut were caught during all months of the year. Differences in catch rates were significant between five trawling strategies and two calendar periods (November–June versus July–October). Pacific halibut bycatch rates were lowest for the trawling strategy for ocean shrimp Pandalus jordani (0.09–0.14 fish/h) and highest for the nearshore mixed-species trawling strategy (0.81–1.46 fish/h). In the deepwater trawling strategy for Dover sole Microstomus pacificus, bycatch rates were high (1.38 fish/h) in July–October at depths between 163 and 320 m and intermediate (0.37–0.50 fish/h) during the rest of the year and at greater depths. The strategy for bottom rockfish Sebastes spp. had relatively low bycatch rates except in July–October at intermediate depths (1.12 fish/h at 163–320 m). Pacific halibut bycatch totals for 1987 and 1992 were estimated by applying logbook effort data to the bycatch rate estimates. In Oregon and Washington the total Pacific halibut bycatch in 1987 was 101.9 metric tons (mt; 95% confidence interval [CI] = 31.6–173.6 mt) for the shrimp trawl fishery and 339.2 mt (95% CI = 111.5–574.9 mt) for the groundfish trawl fishery, and in 1992 it was 57.3 mt (95% CI = 17.9–97.5 mt) for shrimp and 441.2 mt (95% CI = 139.5–753.1 mt) for groundfish. For groundfish trawls in California, the point estimates of total bycatch of Pacific halibut were 79.3 mt in 1987 and 59.8 mt in 1992.