Comparisons of Larval Walleye and Saugeye (Walleye × Sanger Hybrid) Growth and Impacts on Zooplankton in Experimental Ponds

Abstract

Abstract We studied growth differences of larval walleye (Stizostedion vitreum) and saugeye (the hybrid of female walleye and male sauger S. canadense) by monitoring their growth and consumption in hatchery ponds stocked at different densities (10 or 50 fish/m3) and studying concurrent zooplankton dynamics. Walleyes gained more weight than saugeyes, but growth of both walleyes and saugeyes was inversely related to stocking density. At harvest, mean weights of walleyes and saugeyes were 0.67 and 0.57 g for those reared at low density, and 0.32 and 0.23 g for those reared at high density. Stomach content analysis showed that both fish species selectively fed on Daphnia and Cyclops, and also selected for Bosmina when large zooplankton species were less available. In ponds, the biomasses of Daphnia, Cyclops, Diaptomus, and nauphi were greater in ponds where fish density was low than in ponds where fish density was high, but did not differ between fish species stocked. Impacts of fish on zooplankton biomass depend on fish density rather than fish species. We suggest that walleye and saugeye can be managed similarly in hatchery ponds.