MEPS 451:187-200 (2012)  -  DOI: https://doi.org/10.3354/meps09595

ABSTRACT: Increasingly, multispecies interactions are being considered by US management councils during decision making, which highlights the need for identification of fish assemblages across varying spatial and temporal resolutions. On the US West Coast, previous groundfish assemblage analyses have focused either on particular species groups (i.e. Sebastes) or limited time frames and/or geographic regions within the groundfish fishery. The present study expands on previous work to identify groundfish assemblages across the full spatial extent of the West Coast groundfish fishery from 1977−2009, by using 2 fishery-independent trawl surveys. Species assemblages were identified using 2 clustering methods (partitioning analysis and hierarchical analysis) and 2 realizations of the data (presence-absence and log+1 transformed catch-per-unit-effort, CPUE). The analysis using presence-absence data provides information on species that co-occur while the CPUE data provides information on species that occur at similar magnitudes. Temporally and spatially persistent assemblages were detected by both clustering methods through most years. Assemblages identified using CPUE were often subsets of those identified using presence-absence, indicating that the members of an assemblage may occur together, but not necessarily at the same magnitude, a result that should be considered when choosing the clustering metric. Identification of species assemblages is applicable to bycatch models and informative when evaluating the implementation of spatial management measures, and thus germane to current challenges faced by marine resource managers.

KEY WORDS: Cluster analysis · Fisheries management · Multispecies interactions · Catch-per-unit-effort · Marine ecosystems