Changes in bluegill, black crappie, and yellow perch populations in wisconsin during 1967-1991

A common perception among fisheries managers is that the mean size and number of fish within populations has decreased over time. We examined changes in size of bluegills Lepomis macrochirus, black crappies Pomoxis nigromaculatus and yellow perch Perca flavescens in fyke net samples during 1967-1991 to determine changes in size of fish and in creel surveys during 1980-1991 to determine changes in size of fish harvested and total angler catch and harvest. Mean size and proportion of large bluegills and yellow perch in fyke net samples decreased throughout the sample period. Total catch and harvest of bluegills, black crappies, and yellow perch decreased significantly during 1980-1991. Although mean size of bluegills and yellow perch harvested did not change during 1980-1991, the proportion of large bluegills harvested decreased and the proportion of large black crappies harvested increased. We conclude there was a small, but significant reduction in the size of bluegills and yellow perch in the population and a reduction in the mean size of angler harvested bluegills. Results from this study indicate that there appears to be a major shift in size structure in bluegill and yellow perch populations, resulting in smaller, less desirable fish for anglers.