Midwest Fish & Wildlife Conference 2018

AUTHORS. Jeremy J. Pritt, Kevin S. Page, Joseph D. Conroy, Stephen M. Tyszko, Richard D. Zweifel -Ohio Department of Natural Resources

ABSTRACT. Fisheries managers implement minimum length limits (MLL) and bag limits to improve size structure of crappie Pomoxis spp. populations throughout the Midwest and Southeast USA. The success of these regulations has been mixed, including both successful implementations that have met management objectives and others that have resulted in slow growth and stunting of crappies and ultimately regulation removal. Further, evaluations of regulations on crappie fisheries have been limited by narrow time frames at few locations. Consequently, it is unclear whether MLLs and bag limits should be used to improve crappie size structure or where. Ohio implemented a 229-mm MLL and a 30-fish daily bag limit to improve the size structure of reservoir crappie fisheries beginning in 1998 with a single reservoir, expanding to six reservoirs in 2001 and to a total of 43 reservoirs in 2010. Using an extensive, state-wide, standardized population assessment dataset, we sought to determine (1) the response of crappie population abundance (CPE), growth (length at age-2), size structure (PSD), and condition (Wr) to the regulation and (2) whether reservoir surface area and/or productivity mediated the responses. We found that in general, the regulation had a positive effect on population abundance but negative effects on length at age-2, PSD, and Wr. However, the regulation had positive interactions with both reservoir surface area and productivity, such that in large (> 1,000 ha) and productive (total P concentrations > 100 µg/L) reservoirs, crappie length at age-2, PSD, and Wr increased in response to the regulation. These results indicate that the MLL and bag limit could be beneficial in reservoirs with high productivity but counterproductive in small, unproductive reservoirs. Our approach highlights the benefits of extensive, long-term, standardized sampling as we integrated data across years and reservoirs to make comparisons on a state-wide scale.