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Marine Ecology Progress Series

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MEPS 535:213-229 (2015)  -  DOI:

Effects of seawall armoring on juvenile Pacific salmon diets in an urban estuarine embayment

Stuart H. Munsch*, Jeffery R. Cordell, Jason D. Toft

School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat St., Seattle, WA 98105, USA
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ABSTRACT: An important nursery function of estuaries is providing prey resources for juvenile fish. Shoreline armoring compromises epibenthic and terrestrial prey resources, but it is unclear how this affects fish feeding ecology, particularly in urban landscapes where armoring is common. In this study we sampled prey availability and diets from 3 species of juvenile Pacific salmon (Oncorhynchus spp.) in shallow habitats of an extensively armored urban estuary. We compared sites armored by intertidal seawalls with those at small, engineered beaches without armoring. Available prey was different between shoreline types: epibenthic copepods were more abundant and taxonomically diverse at beaches, and barnacles were more abundant at seawall sites. There was no effect of armoring on salmon stomach fullness. Armoring rarely influenced whether salmon selected for or against a prey taxon but did affect diet composition of small (<50 mm) chum salmon (O. keta), which consumed greater abundances of epibenthic copepods at beaches and planktonic copepods at seawall sites. At beaches, these fish selected for epibenthic copepods and against planktonic copepods. At seawall sites, they selected for both epibenthic and planktonic copepods. Armoring did not affect diets of other salmon species or larger chum salmon that had different diets than small chum salmon. Armoring effects on fish diets may depend on differences in prey selection among species and life history stages. Further research is necessary to assess effects of armoring on habitat quality because fish may consume alternative prey when armoring changes the prey field, but it is unclear whether there are energetic costs to the predator.

KEY WORDS: Shoreline development · Seawalls · Armoring · Diet composition · Juvenile salmon

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Cite this article as: Munsch SH, Cordell JR, Toft JD (2015) Effects of seawall armoring on juvenile Pacific salmon diets in an urban estuarine embayment. Mar Ecol Prog Ser 535:213-229.

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