A synthesis of diets and trophic overlap of marine species in the California Current

"A key step toward ecosystem-based management is to better understand how interactions within food webs affect species of commercial and conservation importance. Here we provide comprehensive diet information and food web analysis for major taxa within the California Current ecosystem, including fish, marine mammals, birds, and invertebrates. We synthesized 75 published diet studies from this ecosystem and calculated representative diets for each species or aggregated functional group. We assessed diet relatedness using hierarchical cluster analysis and calculated diet overlaps based on percent similarity index (PSI). Both analyses were performed on functional group data and also separately for each vertebrate species. Cluster analysis identified distinct feeding guilds and revealed both intuitive and novel diet similarities between several species and functional groups. One intuitive example is that functional groups preying on euphausiids, a key forage species in the California Current, show a high amount of overlap. A novel example is the significant diet overlap of shallow small rockfish and baleen whales (e.g., grey whales [Eschrichtius robustus]), both of which consume large amounts of benthic invertebrates. Functional groups were highly significant in explaining the PSI differences between species, which suggests that key ecological interactions will be preserved in ecosystem models that use these functional groups. A visual representation of the complete food web and calculation of food web statistics suggest that there are strong similarities between the food webs of the California Current and the Benguela Current, a similar upwelling-driven eastern boundary current off the southwest coast of Africa."--Exec. summary. Aaron M. Dufault, Kristin Marshall, and Issac C. Kaplan. Format not distributed to depository libraries. "November 2009." Also available online in PDF. Includes bibliographical references (p. 37-44).