A Comparison of Trap Nets and Otter Trawls for Sampling Black Crappie in Two Florida Lakes

Mike S. Allen
Department of Fisheries and Aquatic Sciences, The University of Florida, 7922 NW 71st Street, Gainesville, Florida 32653; (352) 392-9617 ext. 252, Email: msal@gnv.ifas.ufl.edu

Marty M. Hale
Florida Fish and Wildlife Conservation Commission, Eustis Fisheries Research Laboratory. Post Office Box 1903, Eustis, Florida 32727, (352) 357-6635 Email: halem@gfc.state.fl.us

William E. Pine III**
Department of Fisheries and Aquatic Sciences, The University of Florida, 7922 NW 71st Street, Gainesville, Florida 32653; (352) 392-9617 ext. 242, Email: wep@gnv.ifas.ufl.edu

We compared a recreational shrimp Penaeus spp. trawl to trap nets for assessing black crappie Pomoxis nigromaculatus populations. Lakes Griffin and Monroe were sampled with both gears simultaneously during October-December 1997. Coefficients of variation (CV=SD/mean*100) on mean catch-per-effort (CPE) values ranged from 105 to 161 for trap nets and from 62-96 for trawls. Both trawls and trap nets collected fish < 150 mm total length (TL), but trawls sampled significantly more adult fish (> 250 mm TL). Variable catches in trap nets would require more sampling effort (up to four times as much) to obtain precise estimates of mean CPE than trawl sampling. Trawl sampling was preferable to trap nets based on size of fish captured, precision of abundance estimates, cost of the gear, and required sampling effort to estimate mean CPE. However, trawl sampling may be impractical in water bodies with excessive submerged structures, debris, and submersed macrophytes. We are encouraged by the effectiveness of the trawl for assessing black crappie populations in lakes where it is possible to use a bottom-sampling trawl.