Distribution and ecology of crayfish in the Kawartha Lakes region of southern Ontario

Abstract

The distribution, relative abundance, and breeding cycles of seven species of crayfish were examined in the Kawartha Lakes region of southern Ontario. Of the five Orconectes species, whose breeding cycles are remarkably synchronous, the recently introduced O. rusticus has become particularly successful and now occurs commonly in the widest range of habitats where it may be replacing both O. propinquus and O. virilis. Orconectes obscurus, also recently introduced and as yet of very limited distribution, may become similarly successful. Orconectes immunis is found commonly only in the most eutrophic of the lakes, and is therefore not involved in the competition occurring amongst the other four Orconectes species. The two Cambarus species in the region, C. bartoni and C. robustus, are restricted to some of the swifter rapids and falls and to the rocky shores of some of the Shield lakes and, at least in part because their breeding cycles are organized differently, also appear uninvolved in direct competition with the Orconectes species. The success of O. rusticus is likely to be due to a complex combination of behavioral and physiological characteristics.