Abundance, Size, and Recruitment of Pink Salmon ( Oncorhynchus Gorbuscha) in Selected Michigan Tributaries of the Upper Great Lakes, 1984–1988

Abstract

The abundance and size of pink salmon spawners and fry were studied in selected Michigan tributaries of Lakes Huron, Michigan, and Superior from 1984 to 1988. Pink salmon populations in Lake Superior have declined since the early 1980s. In Lake Huron, populations began increasing in 1983 and have leveled off at relatively high numbers. Lake Michigan populations have increased. Male spawners were significantly longer than females in all lakes. Lake Michigan fish were significantly longer than Lake Huron and Lake Superior fish, but no significant difference was observed between the latter two groups. Male spawners averaged 482 mm (1,045 g) in Lake Michigan, 418 mm (574 g) in Lake Huron, and 410 mm (567 g) in Lake Superior. Females averaged 449 mm (840 g) in Lake Michigan, 389 mm (450 g) in Lake Huron, and 388 mm (466 g) in Lake Superior. No significant length differences were observed in outmigrating fry from tributaries of the three lakes. Fry from individual tributaries averaged 31.94 mm (0.138 g) in Lake Huron, 32.64 mm (0.132 g) in Lake Michigan, and 31.96 mm (0.117 g) in Lake Superior. Fry recruitment was variable among years and dependent upon spawner abundance and over-winter flow conditions. Survival estimates from egg deposition to fry outmigration were poor (0.15% to 0.45%), which demonstrates the importance of riverine environments to Great Lakes pink salmon abundance.