The effects of bait type, trap-soak duration, and trap modification on harvest of red swamp crawfish

The effects of bait type, trap-soak duration, and a trap entrance modification were evaluated from February through May 2008 in a 1.29 ha crawfish (red swamp crawfish, Procambarus clarkii) pond in southwest Louisiana. Commercial pyramid traps with three entrance funnels, 1.9-cm square-mesh vinyl-coated welded metal wire, were used. In trial 1, crawfish catch was evaluated in traps baited with Atlantic menhaden (Brevoortia tyrannus), a formulated dry bait, or a menhaden+formulated bait mixture, each at 24-h and 48-h soak durations. In trial 2, the escape of marked crawfish was evaluated in the presence or absence of bait at 24-h and 48-h soak durations. In trial 3, the catchability of traps with modified entrances, designed to reduce crawfish escape, were evaluated at 24-h and 48-h trap-soak durations. In trial 1, menhaden alone was the most effective bait in February and March, all baits were equally effective in April, and the formulated bait alone was most effective in May. Overall, crawfish catch per unit effort (CPUE) with a 24-h soak duration was 36% and 27% higher in number and weight than the 48-h soak. Mean crawfish size increased when trap-soak duration was increased from 24-h to 48-h. In trial 2, traps containing “no marked crawfish” caught significantly more crawfish in both number (37%) and weight (30%) than traps with marked crawfish indicating that the presence of crawfish in traps prior to baiting decreased catch. Mean crawfish escape from traps ranged from 29 to 34%, and the presence or absence of bait had no significant effect on escape; however, the mean escape rate following a 48-h trap-soak duration (39%) was nearly twice that of a 24-h soak (22%). Crawfish CPUE with modified traps was 20% higher with a 48-h trap-soak duration. Modification of the trap entrance funnels with plastic cable ties appeared to reduce the rate of crawfish egress from the traps between 24-h and 48-h