Aggressive Interactions and Resource Competition in Relation to Species Displacement Among Crayfish of the Genus Orconectes

Aggressive interactions and competition for shelter were studied in simplified laboratory environments among the crayfish Orconectes virilis, O. propinquus, and O. rusticus. O. rusticus was clearly superior to O. virilis, with O. propinquus generally intermediate. These results are consistent with ongoing displacements in northern Wisconsin. However, in another part of the study involving competition for preferred substrate, little displacement occurred even at high densities; caution is therefore suggested in assessing the importance of aggressive interactions to species displacements.