What's on the Menu? Evaluating a Food Availability Model with Young-of-the-Year Chinook Salmon in the Feather River, California

Abstract

We adapted a salmonid food availability model by Rader to the Feather River in California and evaluated the ability of the model and two alternative measures of invertebrate abundance to predict the diet of young-of-the-year salmonids. We compared the stomach contents of 240 Chinook salmon Oncorhynchus tshawytscha with the model rankings and the taxonomic abundances in the benthos and drift. Rader's model did not adapt well to the Feather River. The model was correlated with the stomach contents of Chinook salmon but not with invertebrate drift, as theorized by the model's conceptual framework. Invertebrate abundance alone was a better indicator of salmonid feeding, and salmonid diet was correlated with both benthic and drift abundances. We urge caution in applying the model to novel regions and taxa without first examining the correlations between the drift and benthos. Observational studies of salmon foraging behavior, coupled with stomach content and invertebrate collections, may provide more information about food availability in little-studied systems.