Relationship of Planktivory by Shad and Diet Shifts by Young-of-year Largemouth Bass in a Southern Reservoir

The ability of shad populations to impact the density and composition of zooplankton populations has led to the suggestion that planktivorous shad may compete with young-of-year bass for plankton food resources and influence bass recruitment. We studied the feeding dynamics of concurrent year classes of threadfin shad (Dorosoma petenense) , gizzard shad (D. cepedianum) , and largemouth bass (Micropterus salmoides) in a North Carolina reservoir to determine the nature of feeding interactions among the species. Shad planktivory was found to be confined to a brief period early in the growing season coincidental with peak zooplankton densities, after which both shad species shifted to detritivory. Only limited correlations between shad diets and zooplankton dynamics were identified. Patterns of feeding and growth in young-ofyear bass showed no indication that plankton resources were limiting cohort development. Our study provides evidence that young-of-year bass are not directly impacted by shad populations through feeding interactions.

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