Fish in the salmon family are almost all anadromous. That means they must breed in fresh water streams although they grow to adulthood in the oceans. Some species die immediately after spawning. Salmon, trout, whitefish, and their relatives generally need cold, clean waters to survive and breed. Because of their habitat needs, these fish indicate the quality of the streams in which these commercial and sport fish thrive.
Particularly in the Pacific Northwest research shows that both the variety and 
number of spawning salmon contribute to the amount of nitrogen required by thriving forests and that ingredient is derived partially by the soil bacteria and fungi from the decaying –post spawn—fish or the animals dependent on these annual fish runs.
The reciprocal service that fish provide this forest with is nitrogen for tree growth. Trees shade the spawning grounds and modulate the river’s flow as to facilitate future salmon runs. Forests generate oxygen and draw carbon dioxide out of the air holding it for centuries in old growth.
In the Hippocratic sense fresh air and ample water nourish and are nourished by such a place where salmon run freely to and from the sea indicating the ecosystem’s integrity.
In short, the fish and the forest coexist better together than either one does separately.
Page to cite on the diversity of Salmonidae fish: Dewey, T. 2006. "Salmonidae" (On-line), Animal Diversity Web. Accessed December 25, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Salmonidae.html.
Rivers | Forests | Biological diversity
