Ecological roles of crayfish in freshwater and terrestrial habitats

Crayfish are the dominant decapods in many freshwater, and even terrestrial, habitats, playing important community roles through their large size, mobility, behaviour and omnivory. Both density and size affect their ecosystem impacts. Many crayfish require a heterogeneous habitat with refuges for survival of different life stages. Life history patterns can be explained in terms of the selective pressures of the habitat and competition. Crayfish may tolerate broad temperature, dissolved oxygen and salinity ranges. Crayfish key roles and attributes in ecosystems include indicators or surrogates for water quality, bioindicators for communities or habitats, keystone controllers of trophic webs and ecological engineers. Protected crayfish may also act as umbrella species for the conservation of communities. Their main habitat templets are cool or warm high quality streams and lakes, warm lower quality wetlands, semi-terrestrial swamps and temporary wetlands (burrowers), and cave ecosystems. In high quality waters, K selection may be a strong driver, while r selection may dominate in lower quality biotopes.