Lampsilis powellii

Specific name spelling follows that used in the original description (Turgeon et al., 1998).

This species maintains a restricted distribution within Arkansas; suitable habitat has been significantly reduced and continues to be threatened by further habitat alteration and or diminishment of water quality. Probable historical range has been reduced by over 40%, and suitable habitat has been reduced to less than 20% of original; with fewer than 10 viable occurrences remaining.

Range extent used to be >6,000 km2 and now is less than 1,000 km2 based on the current mapped extant populations. Currently, this species is known from the headwaters of the Saline, Ouachita, and Caddo rivers in the Ouachita Mountains of Arkansas. The historical range of this species is not well documented, however based on historical records of other Ozarkian mussels, it is thought that this species could have occurred throughout the entire drainage of these three rivers (USFWS, 1992). Reported collections from Oklahoma and Kansas are thought to be misidentifications.

There are likely no more than ten occurrences globally. In Arkansas, it occurs in Caddo River upstream and downstream of DeGray Lake, upper Ouachita River and South Fork Ouachita River upstream of Lake Ouachita, and the Alum, Middle, North and South forks of the Saline River, as well as the mainstem Saline River downstream to the boundary of the Interior Highlands and Gulf Coastal Plain (Harris et al., 1997; Harris and Gordon, 1987).

Lampsilis powellii has lost much of its habitat to impoundments, channelization, and dredging in many locations on the rivers it inhabits. Many of these rivers have also undergone increased sedimentation from farming and logging and lowered water flow from impoundments and water withdrawal. Water quality degredation by runoff from pesticides, fertilizers, mining, and other anthropogenic sources is responsible for the absence of Lampsilis powellii in much of its historic range. In the Ouachita River, the range has been reduced by the construction of Lakes Ouachita, Hamilton, and Catherine and the hypolimnetic water releases from these impoundments. In the Caddo River, the impoundment of DeGray Reservoir and resulting hypolimnetic water releases have impacted what was probably the uppermost historic habitat for the species in this system. In the Ouachita River, the range has been reduced by the construction of Lakes Ouachita, Hamilton, and Catherine and the hypolimnetic water releases from these impoundments. In the Caddo River, the impoundment of DeGray Reservoir and resulting hypolimnetic water releases have impacted what was probably the uppermost historic habitat for the species in this system. Habitat below DeGray Reservoir is limited in extent. Harris and Gordon (1988) list 16 existing impoundments, one under construction, and one planned within the known range. Harris et al. (1997) cite siltation and sedimentation and a lack of recruitment as threats.