Evaluation of Stocking Walleye Fry and Fingerlings and Factors Affecting Their Success in Lower Lake Oahe, South Dakota

Abstract

Recruitment of stocked fry and fingerlings of walleye Stizostedion vitreum to the population, and influences of available forage and water temperature on stocking success, were evaluated with gillnetting and forage sampling in stocked embayments. Walleye fingerling stocking was found to make a significant contribution to the fall young-of-year population, whereas fry stocking had no effect. Levels of zooplankton biomass increased seasonally from low levels at the time of fry stocking (<30 mg/m3) to much higher levels by the time of fingerling stocking (93 mg/ m3). Water surface temperature correlated closely with zooplankton increases and averaged 15°C at the time of fingerling stocking. Although other undetermined factors (such as predation) may have influenced survival of stocked fish, the zooplankton biomass levels appeared to affect fingerling survival. In addition, low zooplankton levels perhaps were involved in the failure of stocked fry. Abundance of littoral-zone forage fish was not a determining factor in fingerling stocking success.