The Impact of Impoundment on the Mussel Fauna of Kentucky Reservoir, Tennessee River

Abstract

Collections made in Kentucky Reservoir during 1958 indicate that the pre-impoundment assemblage of species, characterized by a preponderance of species belonging to the Unioninae, is doomed; only Quadrula quadrula has adapted to the altered ecological conditions. This species along with two species of Leptodea, one species of Carunculina, and three species of Anodonta comprise the dominant species assemblage in post-impoundment habitats. The impoundment of the waters of the Tennessee River by the TVA has produced a radically altered environment for the survival of the native mussel fauna. The singularly rich pre-impoundment mussel fauna of this area consisted almost exclusively of typical large river forms, many of which are of considerable commercial value; the pigtoe (Pleurobema cordatum) and the niggerhead (Fusconaia ebenus) are the two most abundant commercial species. Present concern for the future of this mussel fauna is evidenced by the 1956-57 study of this resource undertaken by the U. S. Fish and Wildlife Service (Scruggs, 1960). Scruggs' study adequately summarizes the present status of the native pre-impoundment fauna occurring above the area considered here but does not record any mussel invasion of the extensive mud shallows which have resulted from impoundment. Ecologically, the invasion of these virgin shallows is of prime interest and is the subject of this report. Grateful acknowledgment is due Dr. Henry van der Schalie, Museum of Zoology, The University of Michigan, and Dr. Ruth Patrick, Department of Limnology, The Academy of Natural Sciences of Philadelphia, for their generous help and criticism in the preparation of this paper. During October, 1958, sampling was completed over approximately sixteen river miles.2 On TVA Navigation Charts, this area extends from mile 88 to mile 105 and includes the entrance of Duck River. This region is from 4 miles above to 12 miles below Ithe U.S. Route 70 bridge at New Johnsonville, Tennessee. The deep water collections for adult mussels were made with a small crowfoot brail operated by a local clammer. A Peterson dredge was used to, obtain juveniles. In the shallows, hand picking, pollywogging, raking, and screening were employed. The Kentucky Reservoir in the area studied presents three main types of habitats suitable for mussel populations. The first is the old river channel with its firm sand and gravel substrate which gradually is being covered with a deposit of silt; the second is the extensive mud 1 Present address: 1900 Dexter Avenue, Ann Arbor, Michigan. 2 These collections were made under the auspices of the Limnology Department, The Academy of Natural Sciences of Philadelphia.