Morphoedaphic and Biogeographic Analysis of Crayfish Distribution in Northern Wisconsin

We surveyed crayfish distribution and abundance among 67 lakes in the Vilas County area of northern Wisconsin, and then used multiple regression to analyze the relationship between our results and various physical, chemical, and biological variables. The region is dominated by Orconectes rusticus, O. propinquus, and O. virilis, but Cambarus diogenes, Procambarus acutus, and O. immunis are also present; only O. virilis was previously documented from the area. No single variable or combination of variables fully explained variations in crayfish distributions. However, substrate, calcium level, geographic isolation as related to colonization opportunity, and lake size appear to be of general importance. Continuing introductions and competitive exclusion are also probably significant, resulting in a dynamic situation involving an interaction of multiple controlling factors.