Population Dynamics of Walleye (Stizostedion vitreum vitreum) and Yellow Perch (Perca flavescens) in Lake St. Clair, Especially During 1970–76

Abstract

The fish community in Lake St. Clair has remained fairly stable over the past century despite extensive shoreline modifications, a tenfold increase in population in the drainage area, and exploitation from commercial and recreational fisheries. The lake is productive because of its shallowness and fertile drainage basin. The flushing action of clean water from Lake Huron has restrained deterioration of habitat from euthrophication in most areas.Annual commercial fishery landings of walleye (Stizostedion vitreum vitreum) in the 1960s were five times greater than in the previous 50 yr. The larger catches were due, in part, to increased effort, but also reflect a real increase in the walleye population. In contrast, the sauger (S. canadense) declined in abundance through the 1950s and disappeared from commercial landings in the early 1960s. As commercial fishing in Ontario waters of Lake St. Clair was banned in 1970 due to the discovery of high concentrations of mercury in fishes, information on the percid populations was restricted to that obtained from index fishing. Between 1970 and 1976, in association with weak year-classes, the mean age of walleye increased from 2.9 to 5.8 yr. Direct correlations between year-class strength and environmental factors were not evident from the available data. Fishing pressure was reduced considerably after 1970 and is not considered to be an important factor in the low recruitment. The yellow perch (Perca flavescens) population showed no evidence of a change in age distribution during the 1970–76 period. The reasons for the reduction in walleye recruitment after 1970 are not clear, but it is possible that the succession of strong year-classes in the 1960s was exceptional and that the recruitment in the 1970s is closer to the normal condition for walleyes in Lake St. Clair. Key words: Percidae, Lake St. Clair percids, Stizostedion, Perca, population dynamics, exploitation, community ecology