Sustained ecological impacts of invasive crayfish following claw injury

Abstract The rapid acceleration of human-mediated translocation of species has led to the introduction of thousands of species outside their native range with severe consequences for global biodiversity. Freshwater crayfish are a particularly successful group of invasive species as exemplified by the increasingly widespread marbled crayfish. A significant portion of crayfish populations has regenerating or missing claws. At the same time, claws play important roles in e.g., feeding and intraspecific interactions, altering crayfish ability to invade new areas and impact native communities. Here, we combined laboratory experiments and modeling to investigate whether the number of claws on marbled crayfish modulates its ecological impact (focusing on predation rate) using functional response analyses, as well as its intraspecific interactions via population dynamic modeling. We found that the number of claws did not affect the marbled crayfish's functional response type (hyperbolic type II), attack rates, or handling times when preying on chironomid larvae. However, claw numbers had a significant effect on the partial consumption rate of prey, which tended to increase with the number of claws and prey density. The presence of multiple intraspecific predators influenced marbled crayfish non-trophic behavior, with antagonistic effects prevalent between crayfish pairs regardless of claw status. Moreover, the impact of multiple predators was prey density-dependent, with highest levels of antagonism shown at the lowest prey density across crayfish groups. Our findings show that the potential impacts of invasive crayfish was not affected by the number of claws, highlighting the growing context-independent risk that these species pose to freshwater ecosystems.