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Ecology

In the Pacific Northwest and Alaska, salmon are keystone species. The migration of salmon represent a massive retrograde nutrient transfer, rich in nitrogen, sulfur, carbon and phosphorus, from the ocean to the inland freshwater ecosystems. Predation by piscivorous land animals (such as ospreys, bears and otters) along the journey serve to transfer the nutrients from the water to land, and decomposition of salmon carcass benefits the forest ecosystem.

In the case of Pacific salmon, most (if not all) of the salmon that survive to reach the headwater spawning grounds will die after laying eggs and their dead bodies sink to cover the gravel beds, with the nutrients released from the biodegradation of their corpses providing a significant boost to these otherwise biomass -poor shallow streams.