Changes in Growth Rates of Fishes following Reduction in Population Densities by Winterkill

Abstract

Studies were made on four lakes in southern Michigan to determine the effect of the reduction in numbers of fish by winterkill upon the rate of growth of fishes. Earlier investigations on another body of water had demonstrated that a severe reduction in population density had a marked effect on the rate of growth of the survivors. At the time of the winterkill in 1945 scale samples and counts of dead fish were obtained. Samples have been collected each year since the kill. An increase in the rate of growth too great to be accounted for by annual variations followed the winterkill in all but one species from one lake. The increase in growth rate was not maintained, however, for longer than a year in most species. Further studies are suggested to determine possible methods of management which would increase and maintain the greater rate of growth.