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

Abstract

We compared the effectiveness of a recreational shrimp trawl (used for Penaeus spp.) with that of trap nets for assessing populations of black crappie Pomoxis nigromaculatus. Lakes Griffin and Monroe were sampled with both gears simultaneously during Oct–December 1997. Coefficients of variation (CV = 100 × SD/mean) on mean catch per effort (CPE) values ranged from 105 to 161 for trap nets and from 62 to 96 for trawls. Both trawls and trap nets collected fish less than 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 than trawl sampling (up to 4 times as much) to obtain precise estimates of mean CPE. 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 sample with a bottom trawl.