Distribution of Myxobolus scleroperca (Myxobolidae: Myxosporea) in yellow perch (Perca flavescens) in the Great Lakes.

Myxobolus scleroperca infected the sclerotic cartilage of 26 of 100 yellow perch (Perca flavescens) examined in August-September 1991 from the Indiana waters of southern Lake Michigan. The mean lengths of infected and uninfected fish were 171 mm and 148 mm, respectively. A significantly higher percentage of female fish were infected than male because more larger females were examined than males. Perch less than 94 mm were not infected, indicating that the parasite is not evenly distributed in the host population, preferring larger (older) fish. An alternative explanation that should be considered is that young fish die from this infection. Yellow perch collected from eastern Lake Michigan in 1990 and from Saginaw Bay, Lake Huron in 1991 were not infected with M. scleroperca, indicating that the parasite has a patchy distribution among perch populations of the Great Lakes.