Success in Lakes and Failure in Streams: The Rusty Crayfish Invasion

Understanding controls on species invasions is critical to conservation and management of ecosystems. In lakes, invasions of rusty crayfish, Orconectes rusticus, lead to the extirpation of native crayfishes and dramatic changes in ecosystem structure and function. The success of rusty crayfish in lakes had been attributed to its larger relative size. Larger size is advantageous in competition for food, avoiding predation, and reproductive output. Invasion rates and establishment of rusty crayfish in streams, however, has been slower or not successful in some regions. Elevated water flows negatively affected rusty crayfish performance more than native species. Rusty crayfish from high flow conditions exhibited significantly greater streamlining behaviors and performance in flow relative to crayfish from lakes and low flow streams. Crayfish from high flow conditions also exhibited significantly different claw that may facilitate their ability to deal with elevated flow conditions. These results suggest the spread of rusty crayfish in streams may be slower and less successful than predicted from lake invasion models, and that establishment may depend on flow dynamics.