Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Ecology and Evolutionary Biology

Major Professor

David A. Etnier

Committee Members

Dewey Bunting, Paul W. Parmalee, J. Larry Wilson


A 2-year study of the ecology and life history of the snail darter, Percina tanasi, was conducted from 1974 to 1976. The snail darter was found to be a strictly benthic species principally associated with a large river gravel shoal habitat where it feeds and reproduces. Its present range is restricted to the lower Little Tennessee River and a small adjacent portion of the Tennessee River. It is speculated that P. tanasi once occupied a much wider range in the upper Tennessee River drainage which has since been curtailed by impoundments. This species was found to be a short-lived darter which, along with other members of the subgenus Imostoma, spawns in mid-winter. Larval drift is a significant even in the life of the snail darter, and early development is very slow. Adults are migratory, especially during the breeding season. The principal diet constituents are gastropods; there is some utilization of insects. A high degree of selectivity is exercised in procuring the gastropod diet, and there are seasonal trends in both diet composition and consumption levels. P. tanasi occupies a remote position in the Little Tennessee food web. Predation is thought to be high on the eggs and larval stages of P. tanasi but low on adults. Parasitism is very low. The present ecological situation of the snail darter is thought to be considerably altered from that of preimpoundment days. It is threatened with extinction if the remainder of its habitat is inundated by the Tellico Dam.

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