COMPARATIVE REVIEW OF PACIFIC SALMON SURVIVAL RATES

I collated estimates of survival from the literature for naturally reproducing populations of the five major commercially harvested species of Pacific salmon (Oncorhynchus spp.) and compared the mean and variability of survival across species and life-history stages. The conclusion that survival rates can be described with a lognormal distribution was extended to include both the marine and freshwater stages. Average egg-fry survival of pink (O. gorbuscha), chum (O. keta), and sockeye (O. nerka) salmon was similar (average 7%) but was significantly lower than that of coho salmon (O. kisutch, 19%). The egg-smelt survival of chinook (O. tshawytscha) was much higher than coho or sockeye that also rear in freshwater for similar periods (T compared with 1-2%). No direct estimates exist for the marine survival rate of naturally spawning chinook stocks; however, from fecundity and freshwater survival data a species average of 1-2% was derived. Across all species freshwater contributes slightly more to total variation in egg-adult survival than does the ocean, and the schedule of mortality during the egg-adult interval depends on the natural history of each species.