Pike in Rifle, Colorado gravel pit endanger other fish
The fight to protect four endangered species of fish in the Upper Colorado River Basin — an effort spanning three states and involving numerous agencies — has spread to a gravel pit in east Rifle.
At issue is a population of northern pike, a non-native and invasive species, in the pit, which lies in the Colorado floodplain just south of the river and west of Mamm Creek. Shortly after the discovery of northern pike in the Colorado River near Rifle in 2012, Colorado Parks and Wildlife identified the gravel pit as one of the likely sources, along with the Rifle Gap Reservoir.
The fish could pose a significant problem for the local brown trout population, as well as four endangered species of fish further downstream, said Lori Martin, an aquatic biologist with Colorado Parks and Wildlife. Northern pike, she explained, are toward the top of the food chain among freshwater fish, which can lead to population growth in the proper environment.
Since 2012, steps have been taken to reduce the inflow of nonnative fish — including the installment of a screen below the Rifle Gap Reservoir in 2014 and the continued mechanical removal of the pike from the gravel pit — but local, state and federal partners are still trying to come up with a solution that all stakeholders can agree to.
Containing and eliminating invasive species is becoming an increasingly urgent problem here and elsewhere in the Upper Colorado River Basin.
For decades, state agencies, businesses and others stocked water sources with nonnative fish that anglers found desirable, said Brent Uilenberg, Technical Services Division manager with the Bureau of Reclamation Upper Colorado Region. Once people started realizing that these fish were “wiping out the native species,” the attention turned to control and in some cases eradication, he added.
In the case of the Upper Colorado River Basin, those native species include the humpback chub, bonytail chub, Colorado pikeminnow and the razorback sucker — all four are listed as endangered under the federal Endangered Species Act.
Efforts to restore those populations led to the formation of the Upper Colorado River Endangered Fish Recovery Program in 1998. The recovery program brings local, state and federal agencies in Colorado, Utah and Wyoming together with water and energy interests, as well as environmental groups, “to recover endangered fish in the Upper Colorado River Basin while water development proceeds in accordance with federal and state laws and interstate compacts,” according to the program’s website.
A basin-wide strategy — released by the recovery program in February 2014 — for controlling nonnative and invasive species listed the removal of the pike from the Colorado River basin and reservoirs feeding the river as a high priority. That same 160-page report noted that northern pike “are now established in the Colorado River near Rifle and in gravel pits upstream, and will likely invade downstream, rapidly increasing their distribution and abundance if allowed to persist.”
There is growing sense of urgency when it comes to constraining and eradicating invasive species, said Sherman Hebein, senior aquatic biologist for Colorado Parks and Wildlife Northwest Region. All but one of the four endangered species faces a high degree of threat, according to the most recent documents compiled by the U.S. Fish and Wildlife Service. The reports also show that recovery efforts for each fish could come into conflict with economic activities.
“The pond (in Rifle) is an important place and securing it is an important step for us to take,” Hebein said.
However, that step is still a work in progress. The gravel pit — which is privately owned — is located within Rifle’s watershed district, which was created to protect the city’s water supply; primarily the Colorado River. Recovery program agencies, including the Bureau of Reclamation and Colorado Parks and Wildlife, suggested plugging two overflow channels running between the river and the pit, but the city concluded that would not comply with best management practices for the watershed district.
When the original mining plan that led to the creation of the pond was developed, it was designed with overflow channels to keep the river’s water level on par with the pond, explained Jeff Simonson, principal with SGM and contractor for the city of Rifle. Plugging the overflow channels would cause further erosion of the banks during high water, eventually changing the location of the river, which could have adverse on the city’s water intake.
The concerns are valid, said the Bureau of Reclamation’s Uilenberg, but the pike problem persists.
Colorado Parks and Wildlife will continue monitoring and mechanically removing — a process that usually involves setting nets targeted for the species or electrofishing — the pike from the pond and the Colorado River, while the different stakeholders work on determining “the best plan of attack,” Martin said. “At this point it’s still in the early stages.”
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