The use of sex pheromones for the control of invasive populations of the crayfish Procambarus clarkii: a field study

The crayfish Procambarus clarkii is a paradigmatic example of aquatic invasive species. Native to north-eastern Mexico and south-central USA, it has today reached a worldwide distribution. Several attempts have been made to mitigate its impacts but none was successful. In this study, we have investigated in the field whether sex pheromones may be used to control invasive populations of this species. Along two canals of the study area (Padule di Fucecchio, Central Italy, a wetland of conservation concern), in the summer 2006, we installed 18 traps for each of four types, i.e., (1) empty traps as control, and traps containing (2) sexually receptive males, (3) sexually receptive females, and (4) food. The number, sex, and size of the crayfish captured by each trap in 2 days were recorded and compared among types. The results confirm that males are attracted by the females' sex pheromones: the sex ratio of the crayfish captured by the traps containing females was significantly biased towards males. However, when the overall number of the captured crayfish was compared among types of trap, food appeared to be the most attractive bait. The method could be improved using purified and concentrated sex pheromone instead of live animals. The use of pheromones has not been successfully applied to control crustacean decapod invaders so far, and a multidisciplinary approach is needed to face the problem.