Reproductive Performance of Inland Fall Chinook Salmon

Reproductive performance data were collected for inland fall chinook salmon Oncorhynchus tshawytscha from Lake Oahe, South Dakota, in 1988 and 1998. This population exists outside the native geographical range of chinook salmon and completes its entire life cycle in freshwater. Female weights and lengths, total fecundity, relative fecundity (eggs/mm), egg size, and egg survival were all considerably less than reported for anadromous chinook salmon stocks in their native range. Mean weight of spawning females was 2.73 kg in 1988 and 2.01 kg in 1998. Total fecundity was not significantly different at 2,892 eggs in 1988 and 2,496 eggs in 1998. Egg survival to the eyed stage averaged 37.7% in 1988 and 43.8% in 1998 and ranged from 0% to 96%. Relative fecundity (eggs/kg), egg size, and egg survival to the eyed stage were similar for each year. Relative fecundity (eggs/mm of total length) declined from 1988 to 1998. Total fecundity was linearly related to fish length in 1998 and in both years combined. Linear relationships between fecundity and female weight followed a similar pattern. No relationships were observed between total or relative fecundity and egg size. Egg size was also not related to total length or weight. An inverse relationship between egg size and egg survival to the eyed stage was only observed in 1998. Egg survival was not related to total length, weight, total fecundity, or either measure of relative fecundity. This information will help fisheries managers make more efficient decisions, particularly in determining the duration of spawning operations at remote spawning facilities.