Experimental Largemouth Bass Management in Illinois

Abstract

A fishing cycle characteristic of new water-supply reservoirs in Illinois can be predicted with a high degree of accuracy. This sequence of events poses several questions which have been answered at Ridge Lake (18 acres) during the past 9 years, largely through population manipulation during biennial draining for enumeration of the fish. A complete creel census tests the value of population adjustments. In this period of study, fishermen have taken 3,228 largemouth bass weighing 2,385 pounds and 8,169 bluegills weighing 1,168 pounds. Biologists have removed on draining censuses 6,406 small bass weighing 862 pounds and 94,582 small bluegills weighing 4,859 pounds. These fish all originated from 435 bass stocked in 1941, and 129 bluegills stocked in 1944. The hook-and-line yield of bass has varied between 10.9 and 30 pounds per acre per year. Four censuses have indicated that the maximum carrying capacity of the lake for bass was about 50 pounds per acre. When the bluegill population was allowed to expand to 193 pounds per acre, the bass population was depressed to 31.5 pounds per acre. During years when the population of small bass and bluegills was thinned in March, the June reproduction of bass averaged 54,200 schooling fry. In alternate years, when the lake was not drained and contained many small fish of the preceding year, the average bass reproduction was only 5,900 schooling fry. In the alternate years of 1948 and 1950, no schools of young bass were found, no young bass were taken in seining with a 1/8-inch mesh minnow seine in 1948, and only one was taken in 1950. The bass population of Ridge Lake has been maintained at a high level, in spite of the fact that small bass were removed on draining censuses and that since 1945, fishermen have been asked to remove them from the lake when caught. This suggests that legal length limits have no value in bass conservation. The differential in spawning success between years when small fish were removed prior to spawning and years when they were not, casts doubt on the utility of closed seasons and bag limits. Bass have always been protected at Ridge Lake during the spawning season, yet there has been no correlation between the number of bass of spawning size in the lake and the number of young bass produced. In the authorˈs opinion, bass populations in Illinois bear no direct relationship to populations of other fishes, except that they may be depressed by them.