Examination of an effective trap to control North American invasive freshwater crayfish （Procambarus clarkii） in Japan.

Abstract

Japanese conservationists are trying to control the population of North American invasive freshwater crayfish or red swamp crayfish, Procambarus clarkii, which negatively impacts the native water ecosystem in the Japanese Archipelago, by removing them. To compare the efficiency of catching, four types of traps with different shapes （A, Semi-sphere type; B, Cube type or crab trap; C, Net type or shrimp trap; D, Plastic-bottle） werearranged in ponds adjacent Lake Izunuma-Uchinuma, Miyagi Prefecture, Japan. The semisphere type trap （A） showed the highest catching ability. Additionally, to develop more suitable methods for the management of the traps, freshness of bait used for the trap and the frequency of the removal of an entered crayfish in the trap were compared. The freshness of bait in the collecting gear and occurrence of crayfish individuals in cage traps affect to newly entrance of P. clarkii. It is suggested that an effective method for the collection of alien P. clarkii is the use of the semi-sphere type trap and daily maintenance of the cage trap, which involves changing the old bait and removing the trapped individuals.