Pacific salmon spawner escapement goals for the Skagit River watershed as determined by nutrient cycling considerations

Abstract

Wild populations of Pacific salmon (Oncorhynchus spp.) in Washington State are generally at low levels compared to populations that were likely present before the arrival of Euro-Americans in the Pacific Northwest. Habitat loss, the introduction of non-native stocks and species, and overfishing have all contributed to the decline. Historically, huge numbers of salmonid carcasses provided entire watersheds with nutrients derived from the ocean. Diminished populations and transport of these nutrients out of watersheds has caused a nutrient deficiency compared to times when populations were large. This nutrient deficiency may be hampering recovery of salmon and other animal populations. Beginning with the premise that the Pacific Northwest ecosystem evolved to fully utilize massive numbers of spawning salmon, I estimated the biomass of salmon carcasses necessary to support nesting song birds, wintering bald eagles, and salmonid smolt production in the Skagit River watershed in Washington. The proposed spawner escapement goals thus estimated are 150% to 680% higher than current spawner escapement goals for salmon in the watershed. The justifications for these proposed goals include comparison with escapement goals used in other watersheds, the actual uptake of marine-derived nutrients by fish, the impact of increased escapement on subsequent smolt production, and actual relationships between adult spawners and smolts in less intensively fished streams. Actual attainment of these goals will need to consider the physical condition of the watershed and its ability to retain and cycle the nutrients and the social and economic disruption to fisheries that may result from allowing more fish to survive to adulthood and spawn