Numerical definition of groundfish assemblages caught off the coasts of Oregon and Washington using commercial fishing strategies

Numerical definition of species caught together by the groundiish trawl fishery operating off the Oregon and Washington coasts during 1985-87 indicated six major assemblages of species. Observers on commercial vessels. recorded data allowing estimation of the weights of commercially important species caught in each tow. Assem-blages were selected based on consistencies in three types of analysis of the species weights: detrended corre-spondence ordination, two-way indicator species clustering, and Bray-Curtis group average clustering. Two of the assemblages were dominated by a single species, one consisting largely of smooth pink shrimp (Pandalus jordani) and the other primarily of widow rockfish (Sebastes entornelas). The other assemblages identified were a deepwater rockfish assemblage, a deepwater Dover sole assemblage, a nearshore mixed-species assemblage, and a bottom rockfish assemblage. These assemblages of commercially cooccurring species may be treated as units in developing mixed-species management plans. The deepwater rockfish assemblage we identify has not been previously described. La definition numerique des especes capturees par les chalutiers qui pechaient le poisson de fond au large des cBtes des Etats de I’Oregon et de Washington au cours de la periode 1985-1987 a indique six assemblages d’especes principaux. Des observateurs se trouvant sur des navires commerciaux ont releve des donnees per-mettant I‘estimation des poids des especes commercialement irnportantes capturees dans chaque trait. Les assem-blages ont ete choisis en fonction de la conformite dans trois types d‘analyse des poids des especes: ordinatio