Upstream battle for fish
Officials who had hoped to downlist the Colorado pikeminnow this year — a preliminary step toward removing it from the list of endangered species — are putting off the process until 2018.
The Colorado pikeminnow is one of four endangered fish species in the Colorado River. The forebears of the current population swarmed up and down the river in numbers so great that they were dubbed “white salmon.”
Today, though, the pikeminnow is less the top predator and more often the food for non-native predators like the northern pike and smallmouth bass.
That’s particularly true in the Yampa and White rivers, both northern Colorado tributaries that feed into the Green River and then into the Colorado River in Utah.
Colorado pikeminnow, once known as squawfish, are now most common in the Green and Yampa rivers, though the 15-mile stretch of the Colorado River through the Grand Valley is considered critical to survival of the fish.
“We were hoping we were seeing a rebound” in the pikeminnow population of the Yampa River, said Tom Chart, Upper Colorado River Endangered Fish Recovery Program director.
The recent information. however, is that predators have feasted on pikeminnow, holding down the population and putting a damper on plans to downlist the species to threatened for five years to determine whether the species indeed has recovered.
The U.S. Fish and Wildlife Service collects data in three-year “bundles” and the next bundle is due to be complete in 2018, setting that year as a possible marker for downlisting.
The pikeminnow population in the Green River has fluctuated between 2,200 and 4,500 and most recently has been on the increase, said Chart, a fisheries biologist. “But we’re not seeing that positive response on the Yampa.”
Deciding whether to downlist the pikeminnow, or other species, will require significant amounts of data, Chart said.
“As biologists, we need long-term data sets to ensure populations are recovered,” he said. “We know populations will fluctuate naturally through time.”
A case in point is the Colorado River pikeminnow population, which now is between 600 and 800, Chart said.
There has been a recent decline in the Colorado River population, but a data set that goes back to 1992 indicates a “fairly stable population,” Chart said.
The Upper Colorado River Recovery Program is a joint effort among the Fish and Wildlife Service, the states of Colorado, Utah and Wyoming, tribes, conservation organizations and other groups that works to manage the river to recover four species of endangered fish while allowing development of the river.
In addition to the Colorado pikeminnow, the razorback sucker, humpback chub and bonytail are endangered.