Hemistena lata

This species is in a monotypic genus closely related to the genus Elliptio.

This species has been severely reduced through habitat degradation in range to only three widely disjunct populations on two rivers, one of which may no longer be viable; and all of which are represented by a small number of individuals.

This species was once widely distributed in the Ohio, Cumberland, and Tennessee river systems. It ranged in the Ohio River from Ohio downstream to Illinois. In Indiana and Illinois, it was historically known from the White, Wabash (Fisher, 2006), and Tippecanoe Rivers (Cummings and Berlocher, 1990). Kentucky records show it once inhabited the Upper Cumberland, Big South Fork, Green, and Kentucky Rivers. It was historically collected in Tennessee from the Tennessee, Cumberland, Powell, Clinch, Holston, Elk, Duck, and Buffalo Rivers. In Alabama it existed in the Tennessee River presumably across the northern part of the state but all museum records are from Muscle Shoals but is reduced to one population on the Elk River (Williams et al., 2008). Portions of the Powell, Clinch, and Holston Rivers in Virginia also once suppported the species (USFWS, 1990). It has been extirpated from most of its former range but some viable populations may persist in the upper Clinch River in Hancock Co., Tennessee (Parmalee and Bogan, 1998), and Scott Co., Virginia; as well as the Elk River in Lincoln Co., Tennessee (USFWS, 1990). A population in the Powell River in Hancock Co., Tennessee, that was barely surviving in 1979 (3 of 78 sites over 98 river miles) likely is no longer extant or if so, viable (USFWS, 1990).

This species has been reduced to possibly 3 reproducing populations in the Tennessee River system in Virginia (Scott Co.) and Tennessee (Hancock Co.) in the upper Clinch River and Elk River (USFWS, 1990). In Tennessee, viable populations survive in the upper Clinch River (Hancock Co.) in east Tennessee (Parmalee and Bogan, 1998). It is also extant in Elk River, Alabama and possibly at the state line in Tennessee, where densities are very low and viability is questionable (Mirarchi et al., 2004; Williams et al., 2008; Hubbs, 2002).

Impoundments, siltation and pollution leading to water quality and habitat deterioration. Inadequate sewage treatment, coal mining, oil and gas drilling and poor land-use practices. The Powell River watershed was mined extensively for coal, and coal mining impacts are still present, especially in the upper reaches. The lower reaches of the Powell River have large deposits of coal fines and silt. The Clinch River has been adversely affected by pollution and land use practices along the river have contributed to the decline of water quality and loss of mussel populations. It has also experienced some impacts from coal mining. Toxic spills have historically produced mussel kills in the river. Although suitable habitat exists in the Elk River, cold water releases from Tims Ford Reservoir and pollution from unknown sources in the lower Elk River have impacted mussel fauna and reduced density (USFWS, 1990).