Forage Fish Populations and Growth of Muskellunge in a South Dakota Power Plant Cooling Reservoir

The standing crop, age, growth, and impingement loss of forage fishes and the growth rate and impingement loss of muskellunge (Esox masquinongy) were studied to evaluate the use of the Big Stone Power Plant cooling reservoir as an area for rearing and holding muskellunge brood stock. There were 18 species of forage fish present in the reservoir. Sampling indicated that there were 4 major forage fish species. Bluegills (Lepomis macrochirus) made up 68.3% of these species; tadpole madtoms (Noturus gyrinus), 25.8%; orangespotted sunfish (L.humilis), 3.6%; and black bullheads (Ictalurus melas), 2.3%. The estimated total standing crop of the 4 forage species was 28.1 kg/ha. The 1974 year-class was the oldest present among the forage fishes. Most forage fish populations were dominated by age-groups I and II. The growth rates of forage fishes present in the reservoir were similar to those of natural waters in the northern United States. Impingement of forage fishes was restricted predominately to young-of-the-year fishes, except during the winter months. An inverse relationship existed between impingement and monthly water temperature for adult bluegills. Higher impingement rates were noted during evening samples, but only tadpole madtoms were impinged significantly (P \u3c .05) more often at night. Muskellunge were most vulnerable to impingement during the first 2 months following their introduction. Age-group II muskellunge captured in February and March attained a mean TL of 753 mm (700 to 785 mm, range) and age-group I muskellunge captured in February and March attained a mean TL of 465 mm (386 to 575 mm:, range). The growth rate of muskellunge in the Big Stone Power Plant cooling reservoir was higher than those reported for populations throughout North America