Collecting crayfish using a dip net in a stream.

Photographer: C.J. Rice

The eastern United States harbors more than 60% of the world’s currently recognized crayfish species, making it a global ‘hotspot’ for crayfish biodiversity (Richman et al., 2015). The United States and Canadian provinces surrounding the Laurentian Great Lakes are home to approximately 40 crayfish species (Taylor et al., 2015), and a moderate number of these species are rare or have narrow natural ranges (Page, 1985; Taylor et al., 2015; Richman et al., 2015). In the United States and Canada, crayfish species richness generally increases moving south and east. Some states in the southern-most areas of the Great Lakes Region such as Illinois, Indiana, and Ohio have numerous crayfish species with narrowly endemic ranges – the sinkhole crayfish (Faxonius theaphionensis) in central Indiana and the depression crayfish (Cambarus rusticiformes) in southern Illinois are just two examples.

Photographer: C.A. Taylor

Many crayfish species in the Great Lakes Region are only known to occur in streams and rivers, but some species can persist, or even thrive, in lentic waters such as ponds, natural lakes, or reservoirs. An even smaller number of these crayfishes are almost completely terrestrial – they spend most of their lives in underground chambers, removed from direct contact with permanent waterbodies. Unfortunately, non-indigenous crayfish species introduced through human activities present a significant threat to many of the native crayfish species in the Great Lakes and surrounding areas. In some cases, these non-indigenous crayfishes can be considered invasive, given their abilities to rapidly colonize new habitats and displace native species. Invasive crayfishes have already displaced native crayfishes from considerable portions of their ranges and have dramatically altered ecosystem structure in some cases (Wilson et al., 2004). Invasive crayfishes are therefore a formidable threat to both crayfish biodiversity and freshwater ecosystems in the Great Lakes and worldwide (Lodge et al., 2000).

Photographer: Holly Hudson, Chicago Metropolitan Agency for Planning (CMAP)