Size and Age at Maturity of Bluegill (Lepomis macrochirus) in Southeastern South Dakota Impoundments

ABSTRACT

Both social and demographic factors can affect size structure of bluegill (Lepomis macrochirus) populations, but these two factors have not been assessed in South Dakota impoundments. We compared length and age at maturity of bluegill in four southeastern South Dakota impoundments (two with historically low size structure and two with historically high size structure and related bluegill growth patterns to size structure and relative abundance. Despite large differences in size structure and maximum observed total lengths among lakes, all males from three of four populations were mature by age 3, with the only exception being Lake Mitchell (high size structure population; 89% mature). Mean total length at 100% maturity was lower in the two low size structure populations, and bluegill in the two low size structure populations matured at a smaller length than in the two high size structure populations; however, at least 50% of males in all four systems reached sexual maturity by 140mm in all years. Negative relationships between mean catch-per-unit-effort and both proportional size distribution (r² =0.47) and proportional size distribution of preferred length fish (r² =0.86) values for all populations indicated that density-dependence was likely in these systems. Indications of social influence on bluegili behavior were observed; however, density-dependence was likely more influential on size structure.