Definition and analysis of multispecies otter-trawl fisheries off the northeast coast of the United States

Abstract

Otter trawls fished off the northeast coast of the United States catch a variety of demersal and semi-pelagic species depending on the area, depth, and time of year they are used. Because of the relatively non-selective nature of the gear, and biological co-occurrence, fisheries are rarely characterized by an individual species. Fishery management by single-species quota control has thus proved particularly difficult. An alternative approach to fishery definition can be based on determining the spatial/temporal boundaries of relatively unique and homogeneous species compositions, from commercial landings data. Accordingly, operational fisheries were defined by grouping statistical area/depth zone/month categories (n = 576) exhibiting similar species compositions in aggregated commercial vessel trip reports for 1977 to 1979. Based on the results of numerical cluster analyses, 29 mixed-species fisheries (subfisheries) were identified and organized into nine major fisheries reflecting geographic/ecologic zones. A review of historical (1964 to 1980) trends in nominal catch and fishing effort, catch per effort, relative vessel size distribution, and species composition for selected major fisheries is presented. Definition of operational fisheries based on the spatial/temporal variability of species compositions is consistent with most forms of fishery management including total catch and effort regulation, mesh-size restrictions, and seasonal or areal closures. This concept allows managers to implement strategies for optimizing yields from multispecies groups based on various economic and biological criteria (e.g. mesh size resulting in the greatest physical yield from the system), while recognizing that technological and/or biological interactions will result in a mixed-species catch. © 1983, Conseil International pour l'Exploration de la Mer.