Effect of Egg and Larval Survival on Year-Class Strength of Lake Whitefish in Grand Traverse Bay, Lake Michigan

Abstract

A study was conducted in Grand Traverse Bay, Lake Michigan, during 1983 and 1984 to identify factors that are important in determining year-class strength of lake whitefish Coregonus clupeaformis. The major determinants of year-class success were overwintering egg survival and the amount of food available to larval lake whitefish during the first 7 weeks of life, Egg mortality was related to the timing of ice cover, with an early cold winter producing the highest survival. Larval survival was affected by the abundance of available prey, i.e., copepod zooplankton between the sizes of 0.7 and 1A mm in total length. In 1983, when zooplankton of this size were abundant relative to larval fish density, high rates of growth and survival of lake whitefish ensued. In 1984, the prey-per-fish ratio declined greatly, and poor growth and low survival were observed. The dynamics of these early life stages appear to significantly influence both lake whitefish year-class strength and eventual recruitment in Grand Traverse Bay.