Spatial changes in trawl fishing effort in response to footrope diameter restrictions in the US west coast bottom trawl fishery

Changes in the spatial distribution of U.S. west coast bottom-trawl effort in relation to areas of prime habitat for rockfish Sebastes spp. were evaluated between 1992 and 2001. Prime trawlable rockfish habitat (PTRH) was defined based on the spatial distribution of high rockfish catches from logbook data for 1992-1995. Bottom-trawl effort was sharply reduced within PTRH after the establishment of maximum trawl footrope diameter restrictions in 2000. However, reductions in rockfish catch limits prior to 2000 had already reduced trawl activity within these areas, confounding the effects of reduced trip limits and footrope diameter restrictions. Fishing inside PTRH rebounded in 2001, when retention limits for yellowtail rockfish Sebastes flavidus as flatfish bycatch were raised, suggesting that limits may be as important as gear restrictions in determining the spatial distribution of trawl effort in this fishery. The untrawled area of PTRH between 43degreesN and 48degreesN in 2000-2001 was estimated at about 186,000 ha.