Shelter use of the Red-Swamp Crayfish (Procambarus clarkii) in dry-season stream pools

Nonconsumptive predator effects modify crayfish-induced bioturbation as mediated by limb loss: Field and mesocosm experiments

We addressed the implications of limb loss and regeneration for multispecies interactions and their impacts on ecosystem engineering in freshwater stream environments.We included regenerative and nonregenerative crayfish as well as fish predators in a 2 × 2 factorial design to assess the effects on water turbidity of interactions between crayfish ecosystem engineers differing in regenerative status and their fish predators.We demonstrated that crayfish limb loss and predation risks lead to more turbidity in field and mesocosm conditions. Moreover, ongoing regeneration of crayfish increased turbidity, while fish presence seemed to hinder crayfish turbidity-inducing behaviors (such as tail-flipping and burrowing) in the mesocosm experiment.We confirmed that greater numbers of crayfish produce a greater amount of turbidity in situ in streams.Although mechanical burrowing crayfish capacities may depend on crayfish burrowing classification (primary, secondary, or tertiary), our work emphasizes the implication for turbidity levels of crayfish autotomy in freshwater streams.

Agonism and shelter competition between invasive and indigenous crayfish species

Several crayfish species behave as biological invaders. Their establishment in an area has frequently been accompanied by the reduction or elimination of indigenous species. A laboratory study was designed to investigate whether the invasive crayfish Procambarus clarkii (Girard, 1852) is dominant over the indigenous (to Delaware) crayfish Procambarus acutus acutus (Girard, 1852) in either the absence or the presence of a shelter as a limited resource. As expected, we found that P. clarkii is more aggressive than the similarly sized P. a. acutus, thus confirming previous studies that demonstrated an inherent dominance of the invasive over the indigenous crayfish. We then hypothesized that species showing a lower preference for an offered shelter (P. clarkii) should be less motivated to defend it. To the contrary, in a competitive context P. clarkii excluded P. a. acutus from the shelter but did not use the resource. Caution must be used in extrapolating these laboratory studies to the field, and future studies should analyze multiple factors, including the autoecology of the two species and their reproductive potential and recruitment patterns. However, our results might help in highlighting the risks for freshwater biodiversity created by the uncontrolled translocations of P. clarkii and other similar invasive species.