Population Dynamics and Management of Lake Whitefish Stocks in Grand Traverse Bay, Lake Michigan

Abstract

The population parameters and movement patterns of lake whitefish Coregonus clupeaformis in Grand Traverse Bay, Lake Michigan, were investigated in response to an expanding commercial fishery. Tagging data indicated that distinct spawning populations exist in West, Outer, and East bays. Little mixing was observed during the fishing season between the West Bay and East Bay populations, but both contributed to the Outer Bay fishery. The West Bay population was predominantly localized and characterized by a broad age distribution and low exploitation rates. The East Bay population was characterized by a younger age distribution and higher exploitation rates. The Outer Bay fishery mainly consisted offish 4–6 years of age, with intermediate growth and exploitation rates. Biomass in the fishery decreased by 39%, from 439,000 kg in 1986 to 268,000 kg in 1987, because of a combination of increased exploitation and decreased recruitment. Catch quotas (total allowable catch, TAC) for Grand Traverse Bay stocks are dependent upon estimates of recruitment, which is unstable and unpredictable, Calculations of TAC that have resulted, if realized as true harvest levels, could jeopardize the integrity of these lake whitefish stocks. Calculations of TAC can be improved by including an index of the strength of the recruiting year-class.