Cooperative Fish and Wildlife Research Units Program: Missouri
Education, Research and Technical Assistance for Managing Our Natural Resources

Westhoff, J. T., H. A. Abdelrahman, and J. A. Stoeckel. 2023. Upper thermal tolerance of two native and one invasive crayfish in Missouri, USA. Freshwater Crayfish 28:27-36.


The spread of invasive crayfish requires invaded habitats to be thermal suitable and differences in thermal tolerances among species could provide refugia for native crayfish affected by the invader. We estimated upper thermal tolerance for the invasive Faxonius hylas and native F. peruncus and F. quadruncus using critical thermal maxima (CTM) methodology to determine if there are ecologically exploitable differences in estimates among species and if there are areas within their distributional ranges that exceed their thermal maximums. We found no differences in CTM estimates among species or sexes but did observe significant differences in CTM estimates among acclimation temperatures. Additionally, crayfish size had a small, yet significant effect on CTM estimates whereby smaller individuals had lower CTM estimates than larger individuals. The similarity among CTM estimates suggests that for at least upper thermal tolerance, areas thermally available to the native species will also be thermal suitable for the invasive. We did not observe water temperatures in the field that exceeded CTM estimates for any species. However, areas within the mainstem St. Francis River did have warming tolerance estimates of less than 5 °C suggesting spread of the invasive through the mainstem could be limited by water temperature.