Biotic and Abiotic Determinants of Lake Whitefish (Coregonus ciupeaformis) Recruitment in Northeastern Lake Michigan

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Abstract
Comparisons of lifetime average per capita reproductive rates (R0) between stocks of lake whitefish (Coregonus clupeaformis) in Lake Michigan found higher estimates of R0 for rapidly growing exploited stocks than for a commercially unexploited stock. Earlier maturation was the prime cause of this increase. Exploited stocks, however, were dependent on fewer age-classes for reproduction and had a greater potential for instability due to annual variation in recruitment. Overwinter whitefish egg survival in Grand Traverse Bay was nearly fourfold higher during a cold winter with prevalent ice than during the preceding mild, ice-free winter. However, the higher densities of larvae produced during the cold winter experienced greater mortality, with starvation the likely cause. Factors found to influence a stock–recruitment relationship developed for year-classes from 1958 to 1980 included spawning biomass, winter severity (ice-cover), and spring temperatures. Periods of abnormally high and low whitefish catch corresponded to periods in which cold or warm winters were more frequent, respectively. Harvest strategies that dampen naturally caused fluctuations in the spawning stock are recommended.