A novel method for sterilising invasive crayfish: removal of pleopods reduced reproductive success in signal crayfish females

Invasive crayfish impact freshwater ecosystems by reducing macrobenthic diversity and displacing native crayfish through competition and transmission of diseases, such as the lethal crayfish plague. Therefore, effective management strategies must protect biodiversity from invasive crayfish species. One potential control method involves sterilisation of females by removing pleopods, appendages of abdominal segments that, in female crayfish, are involved in carrying eggs. This study aimed to determine how pleopod removal affects female signal crayfish condition and fecundity using a series of laboratory experiments. Females with removed pleopods were compared to the control group and assessed for mortality, moulting, regeneration of pleopods, development of glair glands, and mating and spawning success. The removal of pleopods did not affect survival rate, moulting period, or occurrence of glair glands during the breeding season. Both groups also exhibited a high degree of similarity in mating and spawning activity. Males mated indiscriminately in mixed housing aquaria, indicating that the treatment did not influence their mating activities. Conversely, treated females had significantly reduced fecundity due to compromising the ability to brood fertilised eggs until hatching, the main function of pleopods. Regeneration of pleopods was also noted, but newly grown pleopods exhibited poor function and decreased size compared to pristine ones. Sterilisation by pleopod removal, targeting females, could be applied to all crayfish families, including parthenogenetic species, like marbled crayfish. This research suggests that female pleopod removal could be an effective management strategy for controlling invasive crayfish. It is easy to learn and suitable to be performed by trained volunteers. In-field application of this technique should start from small, closed environments, such as small ponds.