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Terrestrial Ecosystem

When salmon return to spawn and die, choking the shallow streams with their bruised and crimson bodies, they leave behind not only another generation, but a wealth of essential elements that suffuses and energizes a vast web of life, without which the salmon wouldn’t exist at all.

copyright Bruce HamptonOnly recently have researchers discovered that the food webs of salmon-based ecosystems—algae, crustaceans, insects, other fish, birds, otters, even bears—contain nitrogen, phosphorus, carbon, and other organic elements which possess a unique isotopic ratio found only in marine environments. It seems a vast array of terrestrial life in these ecosystems is comprised mainly of oceanic material brought landward by salmon. Given how many plants and animals depend upon its existence, then, scientists term salmon a “keystone” species.

copyright Greg SyversonIn top-of-the-food chain consumers, such as grizzlies and rainbow trout, as much as 80 percent of their bodies are derived from salmon. Even young salmon cannibalize dead adults. In spring the young fish move into lakes and begin to feed voraciously on plankton whose growth is largely dependent on the nutrients from decomposing salmon of the previous year.

So great is this annual accumulation of oceanic nutrients—salmon in Bristol Bay watersheds deposit each year more than one thousand tons of nitrogen alone—that scientists studying core samples from lake and estuarine sediments have been able to reconstruct histories of salmon production dating back centuries.

copyright Bruce Hampton
Also, land plants such as spruce, willow, and alder cycle the life-giving nutrients deposited in excretions from salmon-feasting bears, gulls, and ravens. In some cases, recycled nitrogen and phosphorus from salmon have been partly responsible for the luxurious vegetative growth found along high-altitude streams in Alaska.

copyright Carol Ann Woody
Not surprisingly, it wasn’t long ago that the Yup’ik—who, like other native people of southwest Alaska and throughout the Pacific Rim, consume annually several hundred pounds of salmon per family—were similarly constructed of this lustrous messenger from the sea.