Influence of Reproductive Habitat and Potential Competition on Yellow Perch Populations in Eastern South Dakota Lakes

Yellow perch Perea jlavescens populations often have variable recruitment throughout their range. In eastern South Dakota, glacial lakes with erratic yellow perch recruitment tend to be shallow and lack structure. Because many lakes in South Dakota have limited structure, management efforts may include habitat manipulation as a tool to enhance yellow perch recruitment. The objective of this study was to determine the contribution of eggs deposited on a tree reef toward overall larval yellow perch production in 1,069-ha Lake Madison. Following ice-out in 2000, I placed a spawning reef constructed of 500 conifer trees into this glacial lake. From a 5% sample of trees, I estimated the total number of egg masses deposited on the reef and the mean number of eggs per mass, which together were used to estimate the number of larvae potentially produced on the reef. Using a surface trawl, I estimated the peak abundance of larvae in the entire lake. I examined the proportion of larval yellow perch abundance that was potentially contributed from the reef, which allowed determination of the effectiveness of this spawning reef. Results from two years (2000 and 2001) indicated that the spawning reef may have contributed 14 to 3 7% of the total larval yellow perch hatched in Lake Madison; however, confidence intervals were large. I observed low numbers of egg masses per tree (0.13 to 0.44), which lead me to conclude that several smaller reefs might have been a better design than a single, large reef. More spawning yellow perch used the reef in 2000 than in 2001, perhaps because it was newly introduced habitat. However, high water levels in the spring of 200 1 resulted in newly flooded terrestrial vegetation that likely attracted spawning yellow perch, and possibly caused the decrease in reef use. In both years I observed a gradient in larval yellow perch densities from one end of the lake to the other, suggesting that a large, shallow slough in the northwest corner of the lake may have been used for spawning. Further experimental research would require the use of treatment and control lakes to more accurately assess the effectiveness of spawning reefs. Additionally, growth was determined for 3 5 black bullhead Ameiurus melas populations as part of an initial assessment of their role in the fish communities of eastern South Dakota lakes. Mean length-at-age data were calculated for each population, along with a statewide mean. Results indicated that black bullhead growth was highly variable among populations. Fish up to age 8 were found, though few populations contained fish older than age 6. The means of mean total lengths at ages 1-5 for all populations were 88, 147, 198, 235, and 260 mm, respectively. Growth of black bullheads in South Dakota was similar to other regional growth summaries. Black bullhead growth was most strongly related with bullhead abundance and size structure, was weakly related to habitat, and was weakly related to the population size structure of predators. Growth was positively associated with black bullhead size structure, and negatively associated with black bullhead abundance. Analyses indicated that growth of black bullheads increased with increasing lake depth (maximum and mean), and decreased with increasing productivity (total dissolved solids and morphoedaphic index). Growth was also inversely related to the size structure of predators. My results suggest that there is a regulating factor of density dependence for black bullhead growth, with high density and slow growth in shallower, more productive waters. The potential competitive influence of black bullhead on yellow perch populations was also assessed. B lack bullheads have considerable diet overlap with yellow perch. Additionally, black bullhead populations can attain high biomass levels i n many South Dakota waters. A thigh biomass, black bullheads can possibly exert some competitive influence on other fishes, including yellow perch. To evaluate the potential competitive relationship between black bullhead and yellow perch, I initiated a correlative study of various biological characteristics between the two species. I found little evidence of competition between black bullhead and yellow perch. The few relationships identified were weak, and suggested that competition is unlikely between black bullhead and yellow perch. Yell ow perch growth was actually positively related to the relative abundance of black bullheads suggesting that perch are not adversely affected by high black bullhead biomass. One significant relationship indicated a potential negative effect of black bullhead on age-0 yellow perch. The greatest influence on yellow perch growth appeared to be water body productivity, as measured by total dissolved solids and morphoedaphic index. Yellow perch growth was faster in more productive waters