From CBS Denver (Matt Kroschel):
Colorado Parks and Wildlife set up a camp with more than 20 people working around the clock along the banks of the Herman Gultch in Clear Creek County. They are working to kill all the fish that live in the waterway currently, and then restock that waterway with the greenback cutthroat trout, Colorado’s state fish.
Presumed to be extinct by 1937, several wild populations of what were thought to be greenback cutthroat trout were discovered in the South Platte and Arkansas river basins starting in the late 1950s. According to the CPW, those discoveries launched an aggressive conservation campaign that replicated those populations across the landscape so that they could be down-listed from endangered to threatened under the Endangered Species Act.
Momentum for preserving the native jewels continued to build, and in 1996 the greenback was designated as Colorado’s state fish. Efforts to establish new populations were proceeding along a track that suggested the recovery plan benchmarks might soon be met, and the subspecies could be delisted entirely.
Currently, biologists estimate there are less than 5,000 wild greenback cutthroat in the state, but once this project is complete, they hope to double or triple that number.
“We choose this creek in particular because once we clear out the invasive fish species that live in these waters it will be impossible they will be able to get back into the creek to compete with the greenback cutthroat once we stock them here,” Ken Kehmeier, senior aquatic biologist, South Platte River basin, Colorado Parks and Wildlife, said.
Biologists are using a substance called rotenone to kill the fish that currently call the creek home. They add the liquid upstream of a temporary water treatment and testing center at the bottom of the stream. Once the substance does its job they then dilute and consternate the deadly substance. The process turns the water a purple color for a few hundred yards downstream of the treatment center, but water samples taken downstream from that location show the water quality is back to safe levels as it enters Clear Creek.
Right now, biologists are raising thousands of greenback cutthroats in fish hatcheries in Lake and Chaffee counties.