Stocking Threadfin Shad: Consequences for Young-of-Year Fishes

Abstract
Threadfin shad Dorosoma petenense are commonly introduced into reservoirs to supplement prey available to piscivorous fishes. To determine how early life stages of threadfin shad and their potential competitors and predators interact, we introduced this species into two Ohio lakes—Clark and Stonelick—and evaluated how its young of year influenced young-of-year bluegills Lepomis macrochirus and largemouth bass Micropterus salmoides. After adults were stocked in April, peak abundance of young-of-year threadfin shad occurred in August in both lakes. Bluegills generally spawned earlier than threadfin shad, which apparently reduced competition between young of these species. In Clark Lake, young-of-year threadfin shad did not reduce zooplankton populations, but in Stonelick Lake, peak abundance of young-of-year threadfin shad was followed by a precipitous decline in zooplankton. Data on cladoceran birth rates indicated this decline was due to increased predation by threadfin shad. Survival of bluegill...

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