The Effect of Gizzard Shad on the Fish Population of a Small Oklahoma Lake

Abstract

Abstract Estimates of the standing crop of fish in two small Oklahoma lakes were made by the short-period simultaneous mark-and-recovery method, employing wire traps. The lakes were similar in physical and chemical characteristics, and each contained bluegill, black and white crappie, redear sunfish, largemouth bass, warmouth, black bullhead, and Gambusia. The one lake which also contained gizzard shad, carp, and green sunfish was treated with rotenone to check the accuracy of the population estimate. The lake without gizzard shad had an estimated standing crop of 655 pounds per acre, 608 pounds of which was composed of desirable-sized fish. Recovery from the lake treated with rotenone indicated a standing crop of 1,043 pounds per acre but the weight of desirable-sized fish was 142 pounds per acre less than in the lake without shad. The faster growth, plumper condition, and greater average length of fishes in the lake without shad indicated that direct interspecific competition occurs between centrarchids...