Salmon Bring Nutrients from Ocean to Rivers

G R A N T S   P A S S,   Ore., Feb. 7 -- A growing body of scientific evidence is showing that salmon are more than just a majestic sport fish, a tasty entree, an economic resource or a cultural icon.

From Alaska to California, they serve as a huge natural recycler, responsible for transporting organic material they eat in the oceans and store in their bodies before swimming to the headwaters of watersheds, leaving their rotting carcasses to feed insects, bears, plants, trees and particularly baby salmon.

Bring Nutrients Back to the Rivers

A recent study published in the journal Fisheries figures that as little as 5 percent of the historical biomass of salmon are returning to their native watersheds, creating a dramatic shortage of nutrients derived from the ocean.

The recycling role is so important that restoration of wild salmon in the Pacific Northwest “is hinging on recognition of this issue,” said Jeff Cederholm, a fisheries scientist with the Washington Department of Natural Resources.

Historically, salmon management has been based on allowing the maximum catch in the ocean and rivers while allowing just enough fish to return to their native streams to spawn a new generation.

“We have essentially starved our freshwater systems,” said Bob Bilby, a fisheries scientist with the National Marine Fisheries Service in Seattle.

Based on historical cannery records and published accounts, researchers estimated the annual biomass of salmon returning to rivers before the arrival of settlers in Washington, Oregon, Idaho and California.

They found that salmon runs totaling between 352 million pounds and 497 million pounds had declined to between 26 million pounds to 30 million pounds.

Ecosystem Disrupted

“This means that just 5 percent to 7 percent of the marine-derived nitrogen and marine-derived phosphorous once delivered annually to the rivers of the Pacific Northwest is currently reaching those streams,” the researchers say in their study.