A new alternative technique for sterilising invasive crayfish: removing female pleopods did not alter courtship pheromone release in signal crayfish

Abstract

Invasive species require effective management, especially when population density is still low. Autocidal methods for controlling invasive species offer the advantages of being species-specific and inversely density dependent, without causing environmental changes. An ideal control technique should decrease numbers of juveniles, and, therefore, progressive population ageing. In crayfish, female pleopods can be removed to eliminate support for the attachment of newly fertilised eggs. The aim of this study was to investigate if pleopod removal affects the release of female sexual pheromones. An experiment was performed by exposing signal crayfish males to four waters conditioned by (1) mature females after cutting pleopods (treated), (2) untreated mature females, (3) sexually inactive females, and (4) control water. Males exposed to both treated and untreated mature female waters showed behavioural similarities and increased mating activity compared to males exposed to sexually inactive female or control waters. Removing female pleopods did not affect the release of courtship pheromones, so treated females were still able to attract males by misleading them into mating activity. When females spawn their eggs, they will be lost due to the missing pleopods. Therefore, this method might be considered to control invasive crayfish in management programmes.