Michigan Department of Natural Resources
Fisheries Research Report No 1805, 1973
Response of the Bluegill Population and Fishery of Mill Lake to Increased Growth: a Simulation Model
James C. Schneider
Abstract.-The growth rate of the bluegill in Mill Lake was increased hypothetically from slow to average to fast. New populations were generated with the assumptions that (1) natural mortality is age dependent (Model A) and (2) natural mortality is size dependent (Model B). The populations were then subjected to "fishing" and changes in the size and structure of the population were noted. Catch from the populations was predicted also. Considering the large differences in growth, the differences in the populations and fisheries were small. According to the most realistic model (B), yield in kilograms and average size of bluegills creeled would increase with growth, and the numbers of large bluegills in the population would increase substantially if growth were increased from slow to fast. These benefits may be dampened considerably if the total standing crop of bluegills had to be reduced in order to improve growth. A similar model was constructed for the bluegill population and fishery of Sugarloaf Lake. The characteristics and predictions from that model agreed with empirical data from Sugarloaf Lake.