Michigan Department of Natural Resources
Institute for Fisheries Research Report No. 1788, 1972
Survival, Growth, and Production by Bluegills Subjected to Population Reduction in Ponds
George B. Beyerle and John E. Williams
Abstract.-Survival, growth, and production of bluegills, in populations subjected to yearly reduction were studied in three large, adjacent ponds at Belmont. In Pond 1 (control) the mean standing crop in fall during the 5-year study was 324 kg/ha;2 in Pond 2 (60% yearly reduction of young-of-he-year bluegills) it was 226 kg/ha; and in Pond 3 (90% yearly reduction of young-of-the-year bluegills), 249 kg/ha. Mean yearly reduction in total standing crop was 4% (handling loss) in Pond 1, 33% in Pond 2, and 38% in Pond 3. Survival of young-of-the-year bluegills in Pond 1 was very low (mean of 0.5% per year), compared to survival of young in Pond 2 (mean of 8.1% per year) and Pond 3 ( 12.2% per year). No correlation occurred between calculated egg production and number of young bluegills surviving to fall. Growth of bluegills in all three ponds was very similar; it was also slow, averaging over 25 mm ( 1 inch) less than the statewide average for Michigan. Mean total yearly production in ponds 2 and 3 was similar, and averaged 31% more than in Pond 1. Production by young-of-the-year bluegills in Pond 1 was only 27% of total production, compared with a mean of 58% for ponds 2 and 3. Pond 1 outdid the other ponds in production by year classes other than young-of-the-year. During the study, the number of catchable bluegills per hectare increased from 45 to 351 in Pond 1, decreased from 144 to 126 in Pond 2, and decreased from 169 to 10 in Pond 3.Results of this study suggest that one way to produce larger and faster-growing bluegills in lakes where growth is slow is to keep the bluegill population substantially unbalanced by yearly removal of as much as 50% of the older bluegills, while cropping each new year class down to a level below 10,000 bluegills per hectare.