The Loneliest Sockeye Salmon in the World
There was once a lonely red salmon, we'll call him Larry, who fought his way upcurrent for more than 900 miles, through eight concrete dams, to a lake 7,000 feet above where he started. When Larry reached his destination, he was met with the most frustrating of circumstances--he was the only red salmon to return to the lake. There was no reason to spawn.
Lonesome Larry is the nickname given by a researcher's wife to the only salmon that returned a few years ago to Redfish Lake in the Sawtooth mountains of Idaho. Larry's troubles may have something to tell us about some of the problems facing Alaska's salmon.
Bruce Finney, a paleoceanographer at the University of Alaska's Institute of Marine Science, just returned from Idaho's Redfish Lake, a beautiful lake surrounded by ponderosa pines and snowcapped granite peaks. Finney, a scientist who studies ancient salmon runs by examining the residue fish leave behind, flew down to Washington, Oregon and Idaho to see what he could learn about the sockeyes of the Northwest United States. Sockeyes there are extinct or endangered.
Including Larry, just ten sockeye salmon returned to Idaho's Redfish Lake between 1993 and 1997, making a 900-mile migration from the Pacific Ocean by way of the Columbia and Snake rivers. On the way, those 10 fish were forced up fish ladders around eight dams (four on the Columbia, four on the Snake) and climbed 7,000 feet. As Finney and graduate student Anne Beesley drove mountain roads to reach Redfish Lake, they thought of what it takes for a salmon to make the same trip. "It's a special kind of fish that can withstand that kind of migration," Finney said.
The Columbia River basin sockeyes' decline--from probably more than 4 million to the present 100,000--could be due to a number of reasons. Even with fish ladders, the large dams that have sprung up in their path from lake to ocean make migration difficult. Smaller dams constructed in the early part of the century for private lumber mills, mining operations, and irrigation have blocked the salmons' path. A changing climate also may have affected the salmon. It's hard to pin down a reason for their decline because no detailed records on fish numbers extend past the 1950s, when much of the Pacific Northwest salmon stock was already in big trouble.
That's where Finney's research comes in. Finney and Beesley recently boated to the middle of 15 lakes in the Pacific Northwest to pull a core of the sediment from the lake bottom. That sediment includes traces of nitrogen that were once stored in the living flesh and bone of salmon. Salmon concentrate a unique type of nitrogen in their bodies called nitrogen-15, which is easy for researchers to identify in a lab. After salmon dissolve and release nitrogen-15 into the water, plankton ingest the nitrogen. When plankton die and sink, they leave behind a history of salmon abundance in the layered muck. Using the nitrogen-15 method and by comparing the concentrations to dates determined from deposits of volcanic ash in the cores, Finney can decipher approximately how many salmon lived in the lake at times in the past.
In all but three of these lakes, the sockeye is extinct. Finney hopes to find what year the fish disappeared and wants to compare the ancient sockeye runs in the Pacific Northwest to those in Alaska. He'll also compare the abundance of long-dead sockeyes to the climate to see if any correlations exist. Finney's cylinders of mud could contain unique insights on the decline of Pacific Northwest salmon, and perhaps the recent troubles with Alaska's fisheries.
