Apparently extensive fish mortalities were reported to have occurred in the North Fork Pound Reservoir during February, 1969 and February, 1970. A study was initiated in September, 1969 and continued through October, 1970, in order to ascertain the causes of these mortalities. Chemical water analyses disclosed that the lake pH varied from 4.0-6.4, with a mean near 5.0. The heavy metals, copper, mercury, zinc, iron and manganese were found in the lake waters at levels reported to have chronic effects on fish. Biological investigations revealed fish populations were at low levels (smallmouth bass, channel catfish, largemouth bass, black crappie, green sunfish, bluegill, redear sunfish and brown and yellow bullheads). Reproduction of largemouth bass, green sunfish and black crappie appeared to be nonexistent. Standing crops of zooplankton and phytoplankton appeared extremely low. The reduction of the fishery and the low standing crops of plankton appeared to be due to the toxicity of copper, mercury, zinc and to some extent the toxicities of iron, manganese, and/ or low pH, and low carbonate alkalinity.
