Life History

Salmon spend part of their life in fresh water, and part in salt water. Eggs are laid in the gravel of streams or lakes, and the juvenile salmon hatch the following spring. Pink and chum salmon migrate to the sea that first year, while sockeye, Chinook and coho may stay in freshwater up to three years. Pink and coho salmon only remain at sea for one year, although the other species may spend a variable amount of time in the ocean before returning to their natal stream to spawn.

Many factors may influence freshwater and marine residence time: access to food resources, competition, water temperature and quantity, predation, etc. Variation in life history traits within a watershed has been termed the “portfolio effect” and leads to greater overall resilience in salmon populations.

Researchers working on the Copper River Delta found that 82% of sockeye spent one year in fresh water (36% of all sockeye spent 2 years in salt water, while 46% spent three years in salt water). Only 14% left fresh water habitats after less than a year, and 4% spent two years in fresh water before migrating to the sea. Fourteen years of data across eleven study sites were analyzed, and there was a great deal of variability across years and between sites.

Citation: Powers SP, MA Bishop, S Moffitt and GH Reeves. 2007. Variability in freshwater, estuarine, and marine residence of sockeye salmon Oncorhynchus nerka within the Copper and Bering River Deltas, Alaska. American Fisheries Society Symposium 54:87-99.

© 2011 Copper River Knowledge System