Cambarus robustus

Populations of Cambarus robustus and C. sciotensis in West Virginia and Kentucky are now recognized as a distinct species, C. theepiensis (Loughman et al. 2013). Cambarus ectopistes has been split from the southernmost extent of the C. robustus species complex by Loughman and Williams (2021).

Based on morphology, genetics and zoogeography, several additional populations of Cambarus robustus in Kentucky have also been described as distinct species: populations in the Middle Kentucky River and South Fork Kentucky River are now recognized as C. guenteri; populations in Middle Fork Kentucky River. are now recognized as C. taylori; and populations in the North Fork Kentucky River, Red River, and upper reaches of the Licking River basin are now recognized as C. hazardi (Loughman et al. 2017).

Cambarus robustus is a species of lowest conservation concern. This species has a very large geographic range (hundreds of thousands of sq. km) and is currently described as stable. It is able to occupy a range of habitats including roadside ditches indicating a tolerance to pollution. There are no known major threats impacting the global population although it might be undergoing local declines due to habitat degradation and competition with introduced crayfish in some parts of its range.

This widespread species occurs from southern Ontario east to New York, west to Illinois, and south to North Carolina and Virginia (Hobbs, 1989) and as far south as Tennessee.

Although probably not native east of the Hudson River drainage, records exist for New England including the Thames River drainge in Connecticut (1950s), the Connecticut River, Thames River, Mount Hope Bay drainage systems in Massachusetts, Connecticut and Rhode Island; also populations are known from the West Branch of The Farmington River, Otis, Connecticut; Slocum Brook, Tolland, Connecticut; Dickinson Brook, Granville, Massachusetts; Sawmill Brook, Monson, Massachusetts; and Sucker Brook, Fall River, Massachusetts (Smith, 2000). In New York's Hudson River drainage, Smith (1979) added Rensselaer Co. In Ohio it likely always existed in the preglacial Groveport, Dover, and Pittsburgh River basins, spreading postglacially to Lake Erie and its tributary streams having sufficient gradient (Thoma and Jezerinac, 2000). It is common in Lake Erie tributary streams from Conneaut Creek (Ashtabula Co.) westward to Pickerel Creek (Sandusky Co.), in the Mahoning River, the middle and upper Muskingum River drainages, and eastern tributaries flowing directly into the Ohio River as far south as, but not including: Duck Creek (Washington Co.); all Ohio (Jezerinac and Thoma, 1984). In West Virginia, it occurs throughout the Kanawha River basin, southwestern Ohio River basins, and central portions of the Ohio River direct drains (Loughman and Welsh, 2010). In the Cumberland Plateau, it occurs in Russell Fork (Big Sandy River basin) and the Kentucky River systems where it is very common (Bouchard, 1974). It is widespread in eastern Kentucky from the Kentucky to Big Sandy River drainages (at least 11 locations there); while in the Licking and Kentucky River drainages it occurs only in the upper half of the system (Taylor and Schuster, 2004). Peake et al. (2004) collected this species in the upper Cumberland and upper Kentucky River basins in Kentucky. In North Carolina it is knwon from the New Watauga, and French Broad River basins and Simmons and Fraley (2010) recently collected it at the majority of sites wurveyed within those basins and appears stable. Eversole and Jones (2004) include it for South Carolina just barely getting into Greenville Co.

There are no known major threats for this species. It is likely to be undergoing localised declines due to habitat degradation and loss, however its tolerance to a certain level of pollution makes it less vulnerable to such threats. The species shows an unusually high tolerance to heavy metal pollutants (Taylor et al., 1995).