October 10, 2010
Wednesday PM

Aaron Dupuis lost his fish. Last year, the graduate student installed radio tags on a few dozen whitefish in a maze of lakes near Minto, Alaska. Using a radio receiver, he followed some fish up the Chatanika River to where they spawned, but the location of about 40 others were a mystery. Dupuis’ search for the missing whitefish helped lead biologists to the discovery of an unlikely gathering place “boiling with fish.”

Dupuis, who has since earned a master’s degree from the University of Alaska Fairbanks, searched for his lost whitefish in drainages near where he had previously caught them. Washington Creek. No luck. Tatalina River. Nope. Upper Tolovana River. Not there, either. Then a biologist who has spent much of his career studying whitefish, Randy Brown of the U.S. Fish and Wildlife Service, offered Dupuis a ride in a Cessna about 1,500 feet above the Tanana River.

A section of the Tanana River that is “boiling with fish” in the fall. Biologists recently identified this area as the spawning grounds for many whitefish.
Photo by Randy Brown

“I had all but given up hope finding these fish,” Dupuis said. “(But) over the course of two flights in early October with Randy, I found 30 of the missing 39 fish.”

Dupuis and Brown heard the chirps of the whitefish transmitters coming from a wide, braided area of the Tanana River. A look at the river below showed braids of gray glacial water ripping along in a naked gravel floodplain. Biologists believe that desperate-looking stretch of river is a major spawning area for whitefish.

“(It looks like) a barren wasteland,” Brown said of the stretch of Tanana River just south of Fairbanks. “In the fall it’s mostly just rocks, gravel, drift piles and small channels of silty water, but the deal is that none of the whitefish are feeding during spawning.

“In late September and October this place is full of fish - several species of spawning whitefish, along with suckers, arctic grayling, pike, burbot, and lake chubs,” he said.

This discovery of a major whitefish spawning ground “right under our noses” has Brown and other biologists looking to do what they can to protect it. The Alaska Railroad Corporation is building an extension of the rail line southward that would include a bridge across the Tanana River upstream of the spawning area. Part of the plan involves the mining of gravel from the river for construction materials. In other areas, researchers have shown that scooping gravel from rivers can destroy the nooks and crannies into which fish drop eggs.

Different species of Alaska whitefish, all but the Bering cisco spawn in the Tanana River near Fairbanks
Photo by Randy Brown

The Alaska Railroad Corporation’s current plans include “a series of shallow scrapes rather than a large pit,” in an area outside the spawning habitat Brown and Dupuis identified, said Jim Durst, a habitat biologist with the Alaska Department of Fish and Game.

Brown said that some whitefish that spawn in the Tanana near Fairbanks probably come from as far as the mouth of the Yukon River, more than 1,000 miles away. Decisions made here could affect people who harvest whitefish down the entire river corridor.

“I don’t expect to stop development, but it would be good to understand that this (braided region of the Tanana River) isn’t just a scoured wasteland,” Brown said. “And if you ruin a spawning area, it isn’t coming back, and those fish populations go away. If we know where these areas are, we can divert development projects to places that aren’t so sensitive.”

This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community.
Ned Rozell [nrozell@gi.alaska.edu] is a science writer at the institute.

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