Examining the Effects of Biotic and Abiotic Variables on Crappie Recruitment

Management of crappie populations has been hindered by highly variable recruitment. Often, environmental variables will set recruitment at a particular life stage. Recruitment is affected by any variable that changes reproductive success of adults or growth and survival of young, and these can change through different life stages. Since there are a number of possible variables affecting recruitment, determining which are controlling factors is extremely difficult.  We conducted a multi-lake, multi-year study to more precisely determine the environmental variables driving crappie recruitment. CPUE was calculated and otoliths from a subset of fish were aged and back-calculated to determine age-specific growth for multiple years. Catch curve residuals were used to categorize year classes into high or low recruitment lake-years, then correlated with environmental variables. Recruitment and growth varied greatly across lakes and within lakes across years. Environmental correlates varied across lakes, with water level fluctuation and prey densities playing major roles. In a subset of lakes recruitment was related to the presence of old, slow growing fish, likely related to prey availability. Our data supports that management of crappie should be done on a lake-by-lake basis due to the large variability in environmental effects.