An Estimation of Historic and Current Levels of Salmon Production in the Northeast Pacific Ecosystem: Evidence of a Nutrient Deficit in the Freshwater Systems of the Pacific Northwest
Аннотация:We used historical cannery records and current escapement and harvest records to estimate historical and current salmon escapement to western North American river systems, in order to determine the biomass and marine-derived nitrogen and phosphorous levels delivered by adult salmon, and the deficits corresponding to the diminished returns of adult salmon over the past century. We have estimated the historic biomass of salmon returning to the Pacific Northwest (Washington, Oregon, Idaho, and California) to be 160–226 million kg. The number of fish now returning to these rivers has a biomass of 11.8–13.7 million kg. These numbers indicate that just 6–7% of the marine-derived nitrogen and phosphorous once delivered to the rivers of the Pacific Northwest is currently reaching those streams. This nutrient deficit may be one indication of ecosystem failure that has contributed to the downward spiral of salmonid abundance and diversity in general, further diminishing the possibility of salmon population recovery to self-sustaining levels.
