Nutrients in Salmonid Ecosystems: Sustaining Production and Biodiversity

Nutrient Addition to Restore Salmon Runs: Considerations for Developing Environmental Protection Policies and Regulations

Robert T. Lackey


One scheme to help restore salmon to the Pacific Northwest is the addition of nutrients (i.e., raw or processed salmon carcasses and commercially- produced organic or inorganic fertilizers) to headwaters (e.g., lake or stream salmon spawning and rearing habitat) that are now nutrient deficient because of inadequate replenishment from oceanic or other sources. The rationale is as follows:

Salmon are a vector by which marine nutrients are captured and conveyed against the force of gravity into freshwater ecosystems. Especially in the upper reaches of watersheds where salmon are able to spawn and their offspring spend their early lives, these nutrients, in both organic and inorganic forms, play an important, perhaps essential, role in maintaining viable salmon runs along with numerous other ecosystem components. For example, a substantial proportion of the • nitrogen in plants and animals in streams where salmon are abundant is undoubtedly derived from decomposed spawned salmon. This “anadromous nutrient pump” has been attenuated considerably because salmon runs have been reduced substantially in the Pacific Northwest for decades and, in some places, for more than a century. Thus, the addition of nutrients to watersheds, lakes, or streams where salmon runs are now much reduced would replace, at least partially, the “missing” marine-derived nutrients and would likely enhance salmon runs and overall aquatic productivity.