Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7471
Title: Diet variability of forage fishes in the Northern California Current System
Author: A. D. Hill, Elizabeth A. Daly, Richard D. Brodeur
Publication Year: 2014
Journal: Journal of Marine Systems
Volume: 146
Issue: 5
Pages: 121-130
Keywords: pelagic nekton, forage fish diet composition, juvenile salmon diets, interannual variability, seasonal variability, diet overlap,

As fisheries management shifts to an ecosystem-based approach, understanding energy pathways and trophic relationships in the Northern California Current (NCC) will become increasingly important for predictive modeling and understanding ecosystem response to changing ocean conditions. In the NCC, pelagic forage fishes are a critical link between seasonal and interannual variation in primary production and upper trophic groups. We compared diets among dominant forage fish (sardines, anchovies, herring, and smelts) in the NCC collected in May and June of 2011 and 2012, and found high diet variability between and within species on seasonal and annual time scales, and also on decadal scales when compared to results of past studies conducted in the early 2000s. Prey composition for most forage fish in 2012 was principally composed of copepods, which differed from a preponderance of euphausiids found in the previous studies for cold-water ocean conditions. We also examined diet overlap among these species and with co-occurring subyearling Chinook salmon. Forage fish that show plasticity in diet may be more adapted to ocean conditions of low productivity or anomalous prey fields. These findings highlight the variable and not well-understood connections between ocean conditions and energy pathways within the NCC.