A study of the fish community in the vicinity of a thermal discharge in the James River, Virginia

Abstract

The size, species composition and structure of the fish community in a 9.6 km stretch of the James River in the Piedmont Province of Virginia were analyzed. Twenty collections were made by electrofishing from October 1972 through September 1973 from both the north side of the river, which received a thermal discharge from an electric power station (ΔT4-14C at outfall), and the south side where temperatures were ambient. Parameters investigated were number of species, total number of individuals and the Shannon-Wiener and evenness indices of species diversity. Differences were found to exist in community structure among seasons within both the ambient and thermally influenced zones. In the ambient zone all parameters showed significant seasonal change with values lower in the winter. At the outfall station significant seasonal change occurred for only the diversity and evenness indices with values lower in the summer. Average total abundance remained lower within all seasons at the outfall station than in the ambient zone. As temperatures declined downstream from the point of effluent discharge parameter values more closely approached those on the unheated side of the river.