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Past research has demonstrated that the recruitment pattern of Lake Michigan bloaters (Coregonus hoyi) was best represented by a Beverton-Holt function during 1977-1983. In this present study, we re-assessed relations in bloater recruitment and investigated trends in sex ratio and mean length at age as they related to recent changes in bloater abundance. Bloaters were collected from 1973 to 1997 during lake-wide bottom-trawl surveys and in western Lake Michigan from 1980 to 1998 during graded-mesh gill-net surveys. Length, weight, age, sex, and maturity of bloaters were recorded. The relative abundance of females in the population increased throughout the past 10-15 years to more than 80% in 1997. Relative abundance of females in the population was inversely related to overall abundance during periods of increasing female dominance. Female dominance may be related to an increasingly older population, which resulted from low recruitment, and to the greater longevity of female bloaters. Mean length at age decreased steadily in the 1980s with increased bloater abundance. Bloater recruitment was density dependent and followed a Ricker-type stock-recruitment relation. Future research will focus on identifying other factors that influence bloater recruitment such as the effect of female dominance.
Additional Publication Details
Population dynamics of bloaters (Coregonus hoyi) in Lake Michigan, 1973-1998