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The sex composition and other biological characteristics of the bloater changed substantially during recent decades of continuous ecological change in Lake Michigan. The percentages of females increased from 72% of the bloaters samples in 1928-32 to 95% in 1963, and ranged from 94 to 97% in 1964-69. The unusual predominance of females was established at an early age, unquestionably before age III. Bloaters grew faster in southeastern Lake Michigan in 1960-69 than in 1954 and earlier, and were less abundant there in 1966-69 than in 1962-65. The average age of female bloaters from trawls increased from 3.5 years in 1964 to 6.0 years in 1969. The increase in average age followed a heavy drop in fishing intensity and was accompanied by a decline in recruitment. The percentage representation of age-III bloaters, for example, decreased from 62.4% in 1964 to 2.5% in 1969. The changes in biological characteristics of the bloater may partly be symptoms of a fish population that is poorly adjusted to the changing ecology of Lake Michigan.
Additional Publication Details
Extreme female predominance in the bloater (Coregonus hoyi) of Lake Michigan in the 1960's