Food Habits of Walleye in Shadehill Reservoir, South Dakota

ABSTRACT

The growth rate of walleye (Stizostedion vitreum) in Shadehill Reservoir, a 1,900-ha impoundment in Northwestern South Dakota, is much slower than the statewide average. We investigated the food habits of walleye in Shadehill Reservoir from 1994 to 1995 to determine if the slow growth is prey-related. Walleye were collected at night using electrofishing equipment and experimental gill nets. Of the 201 stomachs examined, 114 contained food. We calculated the relative importance (RI) index to evaluate the contribution of each prey item to the diet. Due to a relatively small sample size and inherent gear biases, data from all seasons were combined and analyzed by length group. The RI analysis indicated that Daphnia spp. was the most important prey for sub-stock length (<25 cm total length) walleye. White bass (Morone chrysops) became increasingly important for longer walleye and was the most important prey for quality- to preferred-length walleyes (38–50 cm TL). Aquatic dipteran larvae were the second most important prey in the diets of quality- to preferred-length walleye, which may indicate limited prey fishes for walleye in Shadehill Reservoir.