Colorado Cutthroat to Return to Native Range | Chemical Treatment of Woods Lake on the Table
by Christina Callicott
Feb 14, 2008 | 274 views | 0 0 comments | 5 5 recommendations | email to a friend | print
SAN MIGUEL COUNTY – The U.S. Forest Service and the Colorado Division of Wildlife are in the planning stages of a project that will attempt to reestablish a population of native Colorado cutthroat trout to Woods Lake and its tributaries. The Colorado cutthroat trout, according to USFS fisheries biologist Chris James, is the only trout species indigenous to the San Miguel River Basin, the Gunnison River and the upper reaches of the Colorado River Basin.

The first step in the project will be to chemically treat Woods Lake in order to eradicate current fish populations, including brook, rainbow and brown trout, which can hybridize with or out-compete the native cutthroat. Once the waters have been cleared, the CDOW will introduce Colorado cutthroat in the hopes of establishing a viable population of this rare fish.

According to Dan Kowalsky of the CDOW, the Colorado cutthroat trout has been lost from up to 90 percent of its historic range in Colorado due to the introduction of non-native fish species, the development of water resources and water quality problems associated with mining. The species has been considered twice for inclusion on the federal endangered species list. It was denied protection as recently as June 13, 2007 when the U.S. Fish and Wildlife Service determined that listing was not warranted. The fish is considered a Species of Concern by the State of Colorado.

Kowalsky said that the primary threat to the Colorado cutthroat comes from other trout species. Due to its evolution in isolated mountain streams and rivers where it was the only trout species, the native cutthroat is at a competitive disadvantage to other species such as brook and brown trout. In addition, rainbow trout hybridize easily with Colorado cutthroat, thereby diminishing the range of the native fish through genetic dilution.

Reintroducing the fish to Woods Lake will expand the species’ range and lessen its chances of extinction, Kowalsky said.

“Our objective with Woods Lake is to create a new conservation population that would add 20 lake acres and five stream miles of new habitat for the species,” Kowalsky said.

Conservation populations are unique for their genetic purity. Kowalsky said the hope is that Woods Lake, which he called “gorgeous fish habitat,” will become a brood lake for stocking other stretches of the San Miguel Basin with wild fish that are adapted to the special conditions of the local habitat.

Because the Colorado cutthroat is so sensitive to other species, it can only be established in areas where it can be isolated from competitors. To that end, the CDOW has created a cement migration barrier at the outlet of Woods Lake to prevent trout in Fall Creek from recolonizing the lake and its tributaries.

A major element of the project will be the treatment of Woods Lake to kill current populations of non-native fish. The CDOW will treat the lake and the upstream tributaries with a pesticide known as rotenone. Registered by the Environmental Protection Agency, rotenone has a long history of use in fisheries management and has also been used for controlling pests such as lice and ticks. Rotenone was used historically in organic agriculture, though sources disagree as to whether current organic regulations allow it.

Traditionally derived from the roots of certain tropical and subtropical plants, rotenone is used by certain native peoples of tropical regions to kill fish for consumption. Rotenone primarily affects gilled species of fish, though invertebrates and amphibians may also be affected. Kowalsky said that invertebrate populations rebound quickly, however, after treatment with the chemical.

Sources agree that rotenone breaks down in the environment within a few days to two weeks, depending on water temperature, pH balance and sunlight. Kowalsky said he expected Woods Lake would be closed for about a week for treatment.

The CDOW will apply a liquid form of rotenone called Legumine, extracted from a leguminous plant of the genus Derris that is found primarily in Peru. Kowalsky said that Legumine was chosen as a more environmentally friendly alternative to some other formulations that contain hydrocarbons such as trichloroethylene, xylene and naphthalene, which have caused public concern in other projects.

According to an informational document published by the American Fisheries Society, “The USEPA has concluded that the use of rotenone for fish control does not present a risk of unreasonable adverse effects to humans and the environment.”

However, the Pesticide Action Network of the United Kingdom cites a study that found a potential link to Parkinson’s Disease; they caution that “the problems evident for rotenone – insufficient usage data, inconclusive studies, concern about unknown synergistic activity with other substances, and potential health hazards, are consistent with problems found with the majority of registered agrochemicals.”

“It’s a dilemma between native fish and the use of chemicals,” James said. “It’s an expensive project and we wouldn’t do it unless we thought it was a good project.”

The Forest Service and the CDOW will host a public meeting on the project April 10, 6 p.m. at the Wilkinson Public Library in Telluride.

Until the lake is treated, the CDOW has suspended the flies-and-lures rule at Woods Lake. When the treatment date becomes certain, Kowalsky will suspend the bag limit as well. Treatment could happen as early as this summer but possibly not until August of 2009.

“Projects like this are essential from an endangered species list point of view,” Kowalsky said. “This is what keeps the Colorado cutthroat trout off the endangered species list.”

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