Fisheries Research Report No. 1792, 1973

Michigan Department of Natural Resources
Fisheries Research Report No. 1792, 1973
The Fish Population of Cassidy Lake, Washtenaw County

James C. Schneider

Abstract.-Cassidy Lake, a warmwater lake in the Waterloo Recreation Area, is typical of many lakes in southern Michigan. In 1964, the size of the Cassidy Lake fish population was estimated, using the mark-and-recapture technique. Fish were caught in seines or trap nets, marked by clipping a fin, and recovered shortly thereafter when the lake was chemically treated. The lake contained 145 pounds of fish per acre. Bluegill (67 pounds per acre), yellow perch (24 pounds per acre), pumpkinseed (14 pounds per acre), and largemouth bass (10 pounds per acre) were the most important species. Fish were growing at rates equal to or exceeding the state average. Recruitment of new fish to the population had been fairly stable for a period of years. Consequently, total annual mortality rates could be estimated from the age-frequency distributions. Total mortality was estimated at 63% for the bluegill, 68% for the pumpkinseed, 80-96% for the yellow perch, and it varied from 26 to 73% (depending on age) for the largemouth bass. The fish population of Cassidy Lake was compared to the fish populations of nearby Sugarloaf and Mill lakes.