Will the experimental population control of an invasive crayfish influence the diet and trophic position of a native crayfish? An assessment using stable isotopes.

Context: Trophic overlap between invasive and native species can cause a competitive displacement of the native. In Australian freshwaters, the invasive crayfish Cherax destructor has proliferated into the ranges of native Euastacus species. Aims: To examine trophic overlap between C. destructor and the critically endangered Euastacus dharawalus and determine whether C. destructor population control causes shifts in the diet and trophic position of E. dharawalus. Methods: We compared δ¹³C and δ¹⁵N values of tissue from both species collected from two sites. Population control of C. destructor was then conducted at one site, whereas the C. destructor population remained uncontrolled at the second site. The δ¹³C and δ¹⁵N values of E. dharawalus were then once again assessed. Key results: Both species occupied similar trophic positions and consumed similar proportions of each food resource prior to control efforts. However, we found increases in the contribution of detritus to the diet of E. dharawalus following the removal of C. destructor , whereas no dietary shifts occurred at the uncontrolled site. Conclusions and implications: The increase in detrital consumption suggests that control of C. destructor increased the availability of a preferred resource. Further, dietary competition between C. destructor and E. dharawalus is likely and reinforces C. destructor representing a substantial threat to Euastacus crayfish. The invasive common yabby has proliferated extensively throughout Australian freshwaters and is likely to compete against native freshwater crayfish over food resources. We assessed whether the fish down of a common yabby population would alter the diet of a critically endangered native spiny crayfish. We found substantial shifts in the diet of the native crayfish following the control of the common yabby population. [ABSTRACT FROM AUTHOR]