Effects of Intensified Fishing, Species Changes, and Spring Water Temperatures on Yellow Perch, Perca flavescens, in Saginaw Bay

A combination of intensified effort and size limit removal in the mid-1960s resulted in exceptional landings of yellow perch, Perca flavescens, from Saginaw Bay. Though gillnet effort increased from insignificance to account for more than half of the annual catch, gillnet catch per unit of effort (CPE) did not decline during the period of intensified fishing (1964–71) despite severe depletion on some grounds. Trapnet landings and CPE peaked in 1966, when the size limit was removed, but by the early 1970s both statistics were only one-third of the 1966 peaks. A fishing-up sequence began in outer Saginaw Bay and the stocks there were depleted. The fishery then shifted to the inner bay, where the stocks also declined, but to a lesser degree. With intensification of the fishery yellow perch growth rate increased, age-groups V–VII were no longer prominent in the catch and females became relatively scarce shortly after attaining vulnerability. The low recruitment of the late 1960s and early 1970s may have been related to the reduced brood stocks.Within the past 35 yr those changes in the fish community which appeared to affect yellow perch most included loss of the walleye, Stizostedion vitreum vitreum, in the 1940s and proliferation of smelt, Osmerus mordax, and alewife, Alosa pseudoharengus, in the 1950s. However, these changes occurred well before the late 1960s, and were probably not involved in the recent yellow perch decline.A comparison of the rate and regularity of the spring warming with the strengths of the strongest and weakest year-classes for the years 1957–75 suggested that spring temperature had an important role in reproductive success. Key words: Percidae, Perca, yellow perch, exploitation, Saginaw Bay, Lake Huron, water temperature, fish community, population trends, history of fishery, Great Lakes