Factors Influencing Bluegill Growth in Small Kansas Impoundments

We evaluated growth of Bluegill Lepomis macrochirus in 24 small Kansas impoundments to understand variability in populations statewide. We assigned ages to 1,323 Bluegill, and when combined, growth parameters using the Ogle-Isermann parameterization of the von Bertalanffy growth model were: L-infinity = 228 mm, K= 0.25, and t(152) = 3.10 y. Growth was variable among the 24 populations and t(152) (time to reach 152 mm total length) ranged from 1.56 to 4.87 y. We selected four representative limnological variables (latitude, maximum depth, total nitrogen, and total phosphorus) and four representative catch variables (catch-per-effort [CPE] of Bluegill, proportional size distribution of 178-mm Bluegill, CPE of stock-length Largemouth Bass Micropterus salmoides, and CPE of Gizzard Shad Dorosoma cepedianum) to elucidate mechanisms that explained t(152) in Bluegill populations. We fit all subset candidate models using the eight variables to predict t(152). Top candidate models (corrected Akaike's information criterion scores within two units of the most parsimonious model) comprised a confidence model set, and we used model-weighted averaging to calculate parameter estimates with 95% confidence intervals for each independent variable present in the confidence model set to develop a single explanatory model. The final model suggested that Bluegill size structure, latitude, and CPE of stock-length Largemouth Bass affected Bluegill growth, whereas a smaller effect was attributed to CPE of Gizzard Shad. Combined, these variables explained 40% of variation in observed Bluegill growth rate. Results from this study summarize Bluegill growth in Kansas and highlight variation in growth rates across small impoundments. Further, they suggest that Bluegill size structure, latitude, and relative abundance of stock-length Largemouth Bass are important factors regulating Bluegill growth in small Kansas impoundments.