Age, Growth and Fecundity of the Alewife, Alosa pseudoharengus (Wilson), in Lake Michigan

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Abstract
This study is based on over 2,000 specimens collected from the Milwaukee area of Lake Michigan over an 18‐month period in 1964 and 1965. The ages of the fish, determined from their scales and otoliths, ranged from 1 to 4 years. The greatest growth‐in‐length, 55.7%, occurred during the first year of life. Growth‐in‐length in succeeding years declined to 24.5% in the second year, 11.2% in the third, and 8.6% in the fourth year of life. The body‐scale relationship is a straight line with an intercept of 21.11 mm on the length axis. Calculated and imperical averages showed that Lake Michigan alewives attained a length of about 95 mm in their first year of life. They reached total lengths of about 139 mm (age group I), 158 mm (age group II), and 172 mm (age group III) in each of the following years. Spawning of Lake Michigan alewives in 1965 extended from the end of June to the first part of August, with the peak occurring in July. The majority of spawning alewives were in age groups II and III. Each female produced from 11,000 to 22,000 eggs. In the ripe alewife, the gonad made up about 5% of the total body weight in the males and about 10% in the females.

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