Rarest Colorado trout gets an assist from biologists

Liz Forster
The Gazette
Armed with a stunner and fish nets, aquatics biologists Cory Noble and Josh Nehring (left to right) with Colorado Parks and Wildlife wade up Bear Creek to capture Greenback Cutthroat Trout on Tuesday, June 13, 2017. In the 1930's, the Greenback Cutthroat Trout was thought to be extinct. But the rare fish was not extinct in the wild, partly because an innkeeper in the 1870's had stocked a pond near Bear Creek with Greenback Cutthroat Trout. The biologists were capturing males and females for the purpose of artificial spawning and eventually increasing the population of the trout by restocking at various locations in the state. The Greenback Cutthroat Trout is the state fish of Colorado. (Jerilee Bennett/The Gazette via AP)
AP | The Gazette

COLORADO SPRINGS, Colo. — Zipped in drysuits, Cory Noble and Josh Nehring led a team of Colorado Parks and Wildlife biologists through a thick maze of tree branches, slick rocks and black flies in Bear Creek Watershed southwest of Colorado Springs. Each carried a tool critical to capturing a greenback cutthroat trout: namely, a net or bucket.

Noble carried something else — a gray plastic box hitched to a backpack with a wire hanging off the back and a yellow wand connected to the front. At first sight, the contraption looks more like a small vacuum cleaner, as opposed to a $10,000 piece of electronic fishing equipment.

As they hiked up the creek, Noble, an aquatics biologist for the Southeast Region of Colorado Parks and Wildlife, swung the wand back and forth across the surface of the water. The wand sent a small electric current through the water, which temporarily stunned nearby fish without harming them. When that happened, Nehring and the three other trailing biologists swept the stunned fish into their nets.

“There’s one!” Noble yelled, signaling his team members to catch the greenback he had spotted in a small pool. Nehring, the senior aquatic biologist for the team, swiftly caught the fish and flipped it over. He then pressed his thumb down the fish’s metallic-colored belly, and a small orange egg popped out of the slit just above the base of its tail. While one single egg might seem inconsequential, for the Parks and Wildlife biologists it could mean another step in the recovery of the rare Colorado fish.

“This is the only place in the planet that this species exists, and we will go to extraordinary efforts to save it,” said Bill Vogrin, the region’s public information officer.

For the past five years, Parks and Wildlife has collected fertile female greenbacks and the milt, or semen, of male greenbacks in Bear Creek every spring to help boost healthy population numbers. The species, which is currently listed as threatened, has been of the highest priority since its listing on the Endangered Species Act.

This year is especially critical, since some of the greenbacks bred in a federal hatchery in Leadville, fish that are later released into one of six watersheds in Colorado, have displayed genetic deformities.

The Parks and Wildlife biologists hope that introducing wild genes to the hatchery’s pool from June’s spawning trips will help combat the deformities. The greenbacks in Bear Creek are the only known genetically pure population in the state, making them even more significant in perpetuating the species.

“We’ve lost quite a bit of natural heritage, and it is our job to restore it,” Noble said. “The type of population decrease we’ve seen in the greenbacks here is not a natural event. Most of it is driven by human interference.”

Noble explained that competition by non-native species introduced for recreation and fish diseases not endemic to North America are also of primary concern.

Noble said that human infrastructure is a major factor in the greenback’s population decline. The redirection of streams to build houses, for example, can eliminate the habitat of both the greenbacks and the insects they eat. Sediment from gravel roads or the soil run-off after fires can also clog their habitats and affect water quality.

Parks and Wildlife found that cars driving up the road to access the trails in the Bear Creek Watershed were pushing enough gravel into the creek to substantially impact greenback populations, leading to the 2012 closure of the road.

“There are no plans to reopen the road, nor do I think there will be anytime soon,” Vogrin said.

Nehring added that years with diminished snowpack do not provide necessary runoff to flush out excess sediment, further impacting habitat.

Last week, about two and a half hours of collection resulted in one “green” female and three “ripe” males. A ripe fish is at its peak spawning time, meaning it will have a viable amount of milt or eggs. “Green” means that the fish could produce milt or eggs, but the biologists are unsure. The biologists said most the fish caught were “spent,” meaning that the female fish has already laid her eggs this season, or that the males have already fertilized eggs.

Back at the trailhead, the team had set up a collection station. Nehring pulled the female out of the bucket and pressed on her underbelly, this time harder than in the creek. There were no eggs other than the first one. She had already spawned. Nehring repeated the process with the males, and they produced a small amount of milt.

“Even one drop of milt can fertilize 1,000 eggs,” Nehring said. “Although we usually hope to catch more fish that are producing more milt, we are still jumping for joy with this.”

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