The Fishery of a Missouri Reservoir Receiving Thermal Effluent

Thomas Hill Reservoir, built by the Associated Electric Cooperative, is located in north central Missouri in a soft coal strip-mine area. Its waters provide cooling for a steam-powered electric generating plant. Fishing pressure averaged 18.2 hours per acre per year during the study. There was a yearly average of 4.9 fishing trips per acre. Anglers averaged 3.9 fish per trip. The average yearly harvest was 21.7 fish, or 13.5 pounds per acre. About 37 percent of all fish caught were taken in the warm-water discharge area mostly during winter. The relationships between angler use, angler success, and fishing pressure and the annual average Secchi disk reading were an important finding of this study. Linear correlations calculated for these paramenters were significant to the five percent level (95 percent confidence). Another important finding of this study was that white crappies were stockpiled during 1969 and 1970, the years of very turbid water conditions, which greatly increased the catch in 1971 and 1972 when the water cleared. The winter catches of fishes in the warm-water arm of the lake were exceptionally good. In 1971, the catch from this 117 acre arm was 689.7 fish per acre. Wind, shallow water, and turbidity characterized Thomas Hill Reservoir. Wave action kept clay particles in suspension and greatly influenced shoreline development. Thomas Hill is the only large Missouri Reservoir that remains frozen through the cold season and should typify other north Missouri reservoirs scheduled for construction.

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