Effects of elevated water velocity on the invasive rusty crayfish (Orconectes rusticus Girard, 1852) in a laboratory mesocosm

Abstract

Invasions of the rusty crayfish Orconectes rusticus (Girard, 1852) in lakes have led to the local extirpation of resident crayfishes and altered littoral communities. The spread of O. rusticus into streams poses an equally serious threat to the biodiversity of resident crayfishes and fishes. We found that O. rusticus in northern Wisconsin streams were significantly smaller than O. rusticus from lakes (P < 0.001) and not significantly different than Faxonius propinquus (Girard, 1852) (P < 0.001) from lakes or streams. We tested time to reach a limited food resource, performance, in 4 water velocities, 5, 30, 50, and 66 cm sec -1, in a laboratory flume. Performance of O. rusticus and F. propinquus did not differ within water velocities, but was reduced in water velocities of 50 and 66 cm sec -1. Performance also did not differ between large and small O. rusticus within water velocity treatments but was also reduced at 50 and 66 cm sec -1. Performance of O. rusticus and F. propinquus from lakes, however, was significantly lower than that of O. rusticus from streams (P < 0.05). In all experiments, performance of crayfish in the 66 cm sec -1 treatment was below 50%, suggesting that this is a critical water velocity for O. rusticus and F. propinquus. Our results also suggest that stream segments with high velocities may reduce upstream dispersal rates of O. rusticus from lakes thus potentially reducing the spread to upstream lake ecosystems.