Evaluation of Smallmouth Bass Introductions in South Dakota Lakes

Abstract

In 1989, electrofishing gear and modified-fyke (trap) nets were used to sample smallmouth bass Micropterus dolomieui during the spring from five lakes of varying environmental characteristics in eastern South Dakota. The\ mean length of smallmouth bass caught by electrofishing was significantly smaller (P=0.0001) than those caught in fyke nets. Highly significant correlations were found between paired mean electrofishing and mean fyke net catch rates among lakes, both for stock- length (18 cm) fish (r=0.973, P=0.005) and all fish ( r = 0.948, P=0.014). These correlations suggest that both gears were not seriously affected by environmental conditions within the ranges encountered. An s posteriori analysis indicated that mean electrofishing catch rates among lakes were 50.1/h over rock/boulder substrates, 7.0/h over sand/gravel substrates, and 0.0/h over silt/organic substrates. Delineation of catch rate data by habitat type indicated habitat use and the influence of habitat differences on overall catch rates. Thus, population density was partially related to available habitat and that standardized sampling programs must consider habitat at sampling stations. In 1990, smallmouth bass were again sampled in the spring from two East River lakes, the mainstem Missouri River reservoirs, and three West River reservoirs. Mean electrofishing catch rates, age and growth, recruitment, size and age structure, and fish body condition from 1989 and 1990 samples were summarized and used to assess stocking efforts, and to provide a preliminary assessment of the need for harvest regulations . Stocking efforts were successful in most waters where rock/boulder habitats were available. Dominant year classes in the samples were not entirely dependent upon the stocking of fingerlings. Differences in growth, variability in recruitment, and a range in total annual mortality could affect size structure and density of smallmouth bass. Hypothetical proportional stock densities (PSD) and densities of quality-length (�180 mm) smallmouth bass were generated from simple modelling to help illustrate these interactions and provide a basis for further assessment of harvest regulations. Limnological data were collected from five eastern South Dakota lakes in 1989 and were examined in relation to smallmouth bass population characteristics. Rock/boulder habitats were a definite prerequisite to the successful establishment of smallmouth bass. Lake morphometry appeared to be related to reproductive success. Lakes with low shoreline development tended to have less potential for reproductive success. However, shoreline development may not be a limiting factor if rock/boulder substrates are already minimal. Potential competition for food may exist between young-of-year smallmouth bass and yellow perch as indicated by age-0 smallmouth bass growth, age-0 and age-1 yellow perch density, and changes in mean length of Daphnia spp. Crayfish densities were low to non-existent where structural complexity of habitat (i.e., interspersion of substrate types) was low and smallmouth bass populations were concentrated