Cage traps and baits for capturing the North American invasive crayfish Procambarus clarkii

To examine appropriate cage traps and baits for capturing the North American invasive crayfish Procambarus clarkii, we conducted two field experiments （Experiments 1 and 2） in a pond in the Handayama Botanical Garden, Okayama, Japan. In Experiment 1, we set three kinds of cage traps （i.e., conger trap, crab trap, and shrimp trap） with the same artificial bait in the pond in late afternoon and then collected them early on the following morning. In Experiment 2, we set and collected shrimp cage traps separately with three kinds of baits, i.e., artificial bait for freshwater fish （Marukyu Co. Ltd., Saitama, Japan）, fish sausage with cheese （Marudai Food Co. Ltd., Osaka, Japan）, and frozen crayfish of P. clarkii, using the same pond and protocol as Experiment 1. In Experiment 1, the number of P. clarkii captured was significantly higher in the shrimp cage traps and conger cage traps compared with the crab cage traps. In addition, P clarkii over a wider range of body sizes including small and large crayfish were captured in the shrimp cage traps compared to the two other kinds of traps. In Experiment 2, the artificial bait was most effective to catch P. clarkii compared to the two other kinds of baits. Our results indicate that of the protocols tested the shrimp cage trap with the artificial bait is the most effective for capture and subsequent eradication of invasive P. clarkii.