Prey Composition and Foraging Ecology As Components of Essential Fish Habitat for West Coast Groundfishes

Determining the prey composition and foraging habitats of U.S. West Coast groundfishes is a mandated but neglected component of the Magnuson-Stevens Fishery Conservation and Management Act.  To address this lack of consideration, we accumulated and analyzed diet composition data for twelve highest-priority groundfish species, as identified in an ongoing review of Pacific Coast groundfish essential fish habitat (EFH). Our research objectives were: to determine (1) diet composition and trophic levels, (2) primary prey taxa, and (3) foraging habitats of each fish species, and to (4) compare ecological roles of these species.  Diet composition and trophic level were calculated using 47 generalized prey categories and proportional weight data, whenever possible. Primary prey taxa were determined based on a novel “Major Prey Index.” We estimated the foraging habitat of each fish species by assigning prey taxa to habitat types, and calculating the relative contribution of each habitat type from diet composition data. Interspecific ecological comparisons were conducted using multiple complementary techniques (e.g., generalized linear models, canonical correspondence analysis). Our findings can be used to inform ongoing and future reviews of Pacific Coast groundfish EFH and fill an important data gap in the habitat-based management of these commercially important species.