Seasonal Variation in Guild Structure of the Puget Sound Demersal Fish Community |
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| Authors: | Jonathan C P Reum Timothy E Essington |
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| Institution: | 1.School of Aquatic and Fishery Sciences,University of Washington,Seattle,USA |
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| Abstract: | Identification of food web linkages is a major aim in ecology because it provides basic information on trophic flows and the
potential for interspecific interactions. In addition, policy and restoration measures mandated to conform to ecosystem-based
management principals can benefit from information on temporal and spatial variability in community-level interactions. Here,
we analyzed guild structure of the demersal fish assemblage in Puget Sound, WA, a temperate estuarine system on the US west
coast. Using diet information from 2,401 stomachs collected across three seasons (fall, winter, and summer), we identified
guild membership for 21 fish species, examined seasonal guild switching, and tested for seasonal shifts in predation and for
differences in the degree of diet overlap at the assemblage level. We accounted for ontogenetic variation in diet by dividing
species into large (L) and small (S) size classes when appropriate. Using cluster analysis and a permutation approach, we
identified seven significant guilds that were typified by predation on benthic invertebrates, pelagic invertebrates, and piscivory.
Of the 18 species with more than one season of diet information, six switched guilds (Pacific sanddab L, sturgeon poacher,
Pacific tomcod S, speckled sanddab, rex sole, and rock sole S). At the assemblage level, we tested for seasonal differences
in prey use between seasons by performing an analysis of similarities based on Bray–Curtis diet similarities and found no
significant difference. However, diet overlap was significantly higher in the summer than the fall and winter (with summer > fall > winter)
indicating that diets within the assemblage converged in the summer. These results indicate that analyses of guild structure
and diet overlap can reveal seasonal variation in community trophic structure and highlight intra-annual food web variation
in the Puget Sound demersal fish community. |
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