Trapping methods for control of non-native red swamp crayfish Procambarus clarkii in a flowing channel

Invasive species, including crayfish, are one of the greatest drivers of change in freshwater ecosystems.The red swamp crayfish (Procambarus clarkii) is an invasive crayfish of particular concern due to the large geographic range where it is established and its ecological effects.Intensive removal efforts can help to reduce invasive crayfish population densities and ecosystem effects, but the most efficient trapping methods vary by study system and target species.We have experimentally investigated trapping methods to design the most efficient program for reducing the population of P. clarkii in a flowing freshwater system.First, we tested the effect of duration that a trap is in the water and found that three nights resulted in the highest Catch per Unit Effort (CPUE; 0.87 crayfish per trap cleared).Second, we tested the catch rates of traps set with different baits and found that hot dogs resulted in the highest CPUE (4.33) compared to four other commonly used bait types (fish, beef liver, dry dog food, and crayfish).Third, we conducted two experiments to test the performance of different trap types.In the first we tested the efficacy of three different trap types and found that nylon mesh traps resulted in the greatest CPUE (2.74) compared to standard traps and tube traps.In the second trap type experiment, we tested the efficacy of standard traps versus two modifications of these traps and found that both modified traps resulted in roughly double the CPUE (standard CPUE 1.13, Mod. 1 CPUE 2.30, Mod. 2 CPUE 2.08).Finally, we determined the distance that P. clarkii travel in our system using a mark and recapture study and found that individuals travel an average of 4.44 m/night.These results can be applied in similar study systems, and/or can serve as a framework for other crayfish removal programs.