Overfishing in a Small Artificial Lake

Onized Lake Near Alton, Illinois

Abstract

The only case of overfishing ever observed in Illinois by Natural History Survey aquatic biologists occurred under conditions favorable for study, 1938-1941. Evidence of overfishing was available from well-kept records of hook-and-line catches for two complete fishing seasons and parts of two others, and from sample catches made with test hoopnets in 1938 and 1940.  A poison census was made on June 24, 1941. At this time the lake contained 9,171 fish weighing 442.17 pounds. The kinds of fish present were largemouth bass, black crappies, bluegills, warmouth bass, green sunfish, yellow bass, black bullheads, yellow bullheads and golden shiners, as well as one carp, one common sucker and one blunt-nosed minnow. The oldest fish were in their sixth summer of life, and nearly all of these were largemouth bass. Most of the fish were taken when in their third summer. In spite of heavy fishing, the natural spawn of fish was obviously sufficient to insure replacement of those fish removed, and under reduced fishing intensity the lake would have returned to its former carrying capacity.