Gene W. Kim and Dennis R. DeVries, Department of Fisheries and Allied Aquacultures, 203 Swingle Hall, Auburn University, AL 36849

Abstract. We used a selective rotenone on gizzard shad (Dorosoma cepedianum) from a 63-ha lake to test hypotheses of cascading trophic interactions and competition between shad and sunfish (Lepomis sp.) larvae. During the second year after shad reduction, we found higher larval sunfish and larval shad densities, lower zooplankton density, and higher algal biomass relative to year one, suggesting cascading trophic interactions. Larval sunfish survival was higher in the second year than the first year, contrary to expectations given the higher shad densities. We tested an alternative hypothesis of larval sunfish mortality due to predation by planktivorous fishes via an enclosure/exclosure experiment using gizzard shad, bluegill (Lepomis macrochirus), and white crappie (Pomoxis annularis) as predators and zooplankton as alternative prey. Relative to fishless controls, larval sunfish mortality was higher in bluegill and crappie treatments while the shad treatment did not differ from fishless controls. Predation by crappie appeared to be size-specific, as indicated by small larvae (3-7 mmSL) having higher mortality than large larvae (8-18 mmSL). In contrast, for bluegill predators large larvae suffered higher mortality than small larvae. Given these results, we suggest that recruitment in freshwater systems is likely influenced by both competition and predation, similar to results from marine systems.