Chickamauga Reservoir Mussels 87 



than F. subrotunda in the middens, is presently a common component 

 of the Chickamauga Reservoir naiad fauna. With reference to Obovaria 

 retusa (Lamarck 1819), Ortmann (1925:348) commented that "In the 

 upper Tennessee it goes to Knoxville region, but is very rare." With the 

 exception of one Late Woodland site, valves of this distinct species were 

 recovered from all sites, but totaled < 2% for all samples. As a species it 

 appears on the verge of extinction; a few old relic specimens are occa- 

 sionally taken below Pickwick Dam and in the middle Cumberland 

 River, Tennessee (Parmalee and Klippel 1982). It is now extirpated in 

 the middle and upper Tennessee River. 



Valves of a few species typical of small-to-medium size rivers, such 

 as Fusconaia barnesiana (Lea 1838), Lampsilis fasciola (Raf. 1820), 

 Lemiox rimosus (Raf. 1831), Obovaria subrotunda (Raf. 1820), and 

 Ptychobranchus subtentum (Say 1825), occurred sparingly in some of 

 the middens. Combined shells of these species comprised < 1% of all 

 samples. Only eight valves of Ligumia recta (Lamarck 1819) were reco- 

 vered (six in 40MG50, a Mississippian site). Although fairly common 

 and widespread throughout the Tennessee River and its major tributar- 

 ies today, this species was apparently a rare shell in the middle and 

 upper Tennessee during aboriginal times. Cyprogenia irrorata (Lea 

 1829) is another species once widely distributed throughout the Ohio, 

 Cumberland, and upper Tennessee River drainages. It occurred in most 

 of the Chickamauga Reservoir middens, but sparingly. Warren (1975) 

 identified 127 valves of this species (only 0.39% of the total) form the 

 Widows Creek site. Cyprogenia irrorata, like most species adapted to 

 riffle and shoal habitats in the Tennessee River, has been extirpated or 

 reduced to relic populations of old individuals in river sections affected 

 by impoundment. 



Recent Adaptations to Impoundment 



Impoundment generally produces a reduced rate of current flow, 

 increased water depth with often daily or seasonal extremes in water 

 level and temperature fluctuations, and siltation. The adverse effects 

 these conditions can exert in extirpating a species or reducing it to a few 

 nonpropagating individuals have been discussed. The fate of at least a 

 dozen species within the genus Plagiola provides ample documentation. 

 On the other hand, changes in the aquatic habitat brought about by 

 impoundment and the establishment of a "river-lake" has proved favor- 

 able to several species. Bates (1962) discussed this phenomenon for the 

 lower Tennessee River (Kentucky Reservoir). Three species of Anodonta 

 — A. grandis (Say 1829), A. imbecillus (Say 1829), and A. suborbicu- 

 lata (Say 1831) — have now become well established locally in the shal- 

 low mud-bottom bays and/ or shorelines throughout most of the reser- 

 voirs. No valves of Anodonta were recovered in the Chickamauga 



