Numerical Definition of Groundfish Assemblages Caught Off the Coasts of Oregon and Washington Using Commercial Fishing Strategies

Abstract

Numerical definition of species caught together by the groundfish 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. Assemblages were selected based on consistencies in three types of analysis of the species weights: detrended correspondence 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 entomelas). 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.