Reproductive Tactics of Walleye (Stizostedion vitreum) in Lake Erie

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Abstract
The average age of mature female walleye (Stizostedion vitreum) (5 yr) assessed in October or November is about 1 yr younger than the average age of spawners (6 yr) collected in April of the next year. To determine why there was a delay in the age at first reproduction, walleye were collected in western Lake Erie and the Thames River. Energy stored in the form of fat increased exponentially with body weight. Gonad size increased linearly with body size, the ovary constituting a relatively constant 18–22% of total body weight over all body sizes. Although allometric relations constrain energy acquistion and allocation, ecological conditions (water temperature and prey availability) affect variability within those bounds. Surplus energy (stored energy minus energy allocated to gonads and metabolism) was increasingly available for females greater than 2 kg, corresponding to females older than 5 yr. Thus, age at first reproduction is influenced by the physiological constraints on acquiring and allocating energy and by the energetic demands of spawning. Energetic condition of the spawning stock was associated with year-class strength. The strong 1991 year-class was produced by females with greater surplus energy than the spawners of the weak 1992 year-class.

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