Effects of environmental factors and sport fisheries management practices on largemouth bass (Micropterus salmoides) fluctuations in abundance in Illinois inland lakes

0Four theoretical models were developed relating environmental factors, anthropogenic factors, productivity (fish caught per hour of electrofishing sampling), and recruitment to several measures of the abundance of largemouth bass (Micropterus salmoides) in inland Illinois lakes. Environmental predictors tested were precipitation amounts scaled for lake, watershed size, and land use practice, growing and cooling degree days, snow depth, lake conductivity, and variables for lake morphology. Lake morphology variables were represented by the percent of lake volume in the euphotic zone, shoreline habitat type, and lake inshore mean depth. Anthropogenic predictors tested were largemouth bass stocking, lake rehabilitation events, water level manipulation practices, aquatic vegetation controls, fish length limit changes and fish removal practices.; Four response variables were derived from the number of largemouth bass caught with electrofishing gear during fall sampling. All raw catch-per-effort data were corrected for catchability and logarithm transformed. One-year-old fish (age-1 response variable) was used for all predictors of the anthropogenic component except changes in length limit. Fish 300 mm and larger (adult response variable) was used for changes in length limits. Average lake catch-per-effort was used to derive the response variable for factors potentially explaining differences in lake largemouth bass abundances. Recruitment at age-2 was the response variable for investigating effects of natural factors on recruitment.; Linear regression was used to analyze predictors' effects on the response variables. Each anthropogenic predictor was analyzed for main effects and first-order interactions with the environmental predictors. Multiple-lake (for broad-based treatment effects) and lake-specific analyses of the anthropogenic component were performed. Anthropogenic factors accounted for more variability in response variables than environmental factors. The age-1 response variable decreased the first year and increased the second year following lake rehabilitation. The adult response variable increased following the imposition of all length limits. None of the predictors analyzed accounted for differences in lake productivity. Recruitment at age-2 correlated only with age-1 abundance.