UW Researchers Work to Preserve Yellowstone Lake's Native

Oct. 8, 2004 -- Researchers from the University of Wyoming's Department of Zoology and Physiology are collaborating with the National Park Service to resolve a crisis that threatens Yellowstone National Park's cutthroat trout population.

They are studying the ecosystems in and adjacent to Yellowstone Lake. One team is researching reproduction of lake trout, an efficient predator that consumes cutthroats. Two other teams are studying how the cutthroat trout's decline affects tributary streams and terrestrial habitat.

"The once valued pursuit of cutthroat trout fishing in Yellowstone Lake is declining and opportunities for visitors to see wildlife, such as otters, osprey and grizzlies, are being reduced," says Wayne Hubert, fish biologist with the Wyoming Cooperative Fish and Wildlife Unit based at UW. "Once we have a better understanding of the surrounding ecosystems and how they work, we can come up with management strategies."

The native Yellowstone cutthroat trout have been in a sharp decline and it may be largely due to the 1980s illegal introduction of lake trout. Additionally, whirling disease and four years of drought may be contributing to the decline, Hubert says.

Yellowstone Lake is home to 80 percent of the remaining population of Yellowstone cutthroat trout, one of 14 sub-species of cutthroats, according to Lusha Tronstad, a UW doctoral degree candidate in zoology and physiology.

Patricia Bigelow, NPS biologist and UW doctoral student being advised by Hubert, is working to characterize lake trout spawning habitat. She will identify locations in Yellowstone Lake where lake trout may colonize in the future. To date, three locations in the West Thumb Geyser Basin have been identified as significant lake trout spawning areas, according to Hubert.

Tronstad and Robert Hall, a UW stream ecologist, are studying the decline in nitrogen that is transported by cutthroats during spawning migrations into tributary streams.

"One stream we are monitoring is Clear Creek, which in the past averaged 30,000 cutthroats spawning," says Tronstad. "This summer, about 1,000 fish spawned, which means far less nutrients are coming into the stream and it is potentially less productive."

Jamie Crait, a UW master's degree student in zoology and physiology, is being directed by Merav Ben-David, a UW wildlife ecologist, to determine what the cutthroat trout reductions mean to the North American river otters, animals that regularly feed on cutthroats. They are studying the otters' role in transporting nutrients from Yellowstone Lake to forests.

Crait explains that otters acquire nutrients from fish, such as nitrogen, phosphorus and carbon, and move them into forests.

"When you disrupt the ecosystem, you lose another venue of forest fertilization," Ben-David says.

She says this is the first comprehensive study of river otters in the Greater Yellowstone ecosystem, which limits the researchers' ability to link the cutthroat decline to actual declines in otter numbers. They believe otter activity in Yellowstone National Park appears lower than in other Rocky Mountain areas.

The research teams plan to publish articles in respected scientific journals and provide NPS management with information on other facets of the Yellowstone cutthroat trout crisis. The research endeavors are funded by NPS and the Environmental Protection Agency.

"The NPS has been very supportive," says Crait. "We couldn't do our research without their help."

The NPS, which issues an annual report on the Yellowstone fisheries, collects long-term fish data and manages the lake trout through gill-netting.

For more information, call NPS Supervisory Fisheries Biologist Todd Koel at the Yellowstone Fisheries office at (307) 344-2281.

Posted on Friday, October 08, 2004