Early survey results suggest decent spawning and survival rates
By Bob Berwyn
SUMMIT COUNTY — Cooperation between water users and state and federal agencies — as well as timely summer rains — helped maintain flows for four native and endangered Colorado River fish this summer.
While the Upper Colorado River Endangered Fish Recovery Program wasn’t able to meet its dry-year flow goals of 810 cubic feet per second at Palisade, Grand Valley and upstream water managers worked cooperatively to maintain an average flow of 500 cfs this summer, well above the flows during Colorado’s last significant drought in 2002.
And warm temperatures in the river, while not optimal for non-native trout, may have helped some of the young endangered fish like the Colorado Pikeminnow put on a bit of extra weight, a key factor to surviving their first winter, said Tom Chart, director of the interagency recovery effort.
“Everybody breath a sigh of relief when September came around,” Chart said. “We were in a better position with upstream reservoir storage … and we managed to limp through.”
First results from late-summer monitoring in the Lower Colorado River and the Green River suggest that spawning numbers and initial survival rates for Colorado pikeminnow were near average, despite drought conditions, Chart said, adding that the size of the young fish was above average — good news for the fish going into the winter.
Chart said biologists were mostly able to meet their targets for removing non-native species like smallmouth bass, considered a primary threat to the endangered species. The same warm conditions that helped pikeminnows thrive this summer were also beneficial to spawning smallmouth in the Yampa River, so continued efforts at controlling the non-natives is crucial, he explained.
Chart said field biologists also spotted some young razorback suckers this summer, which is rare. The sightings may confirm that the number of spawning adults has increased during the past six or seven years.
“That’s good news on that front,” Chart said. “We may be reaching a critical mass in the number of adults.”
The recovery program is also experimenting with stocking a larger size of bonytail chubs to try and promote a higher survival rate.
The long-running recovery effort for the endangered fish — Colorado pikeminnow, razorback sucker, bonytail and humpback chub — covers the entire Upper Colorado River Basin, but program managers focus on a 15-mile reach of critical habitat from Palisade to the confluence of the Colorado and Gunnison rivers as they try to coordinate reservoir releases and irrigation diversions.
The fish have evolved to survive a wide range of extreme conditions found in the Colorado River naturally, but impacts from dam building, diversions and channelization pushed the fish toward the brink of extinction.
This summer, program managers credited various water users with making an extra effort to sustain the recovery effort.
For example, the Orchard Mesa Irrigation District strategically operated a structure in the Grand Valley Power Plant discharge canal to make this water available for the Grand Valley Irrigation Company. That helped preserve stored water in Green Mountain Reservoir, benefiting all Colorado River water users in the state of Colorado and leaving the reservoir in a better condition respond to continued drought conditions.
“A lot of credit for having water available in western Colorado this year goes to having storage reservoirs available with skilled operators who managed flows as well as could be expected given the drought conditions,” said Orchard Mesa Irrigation District manager Max Schmidt.
The Grand Valley Irrigation Company took advantage of low flows to remove a cobble bar in the river that prevented operation of a fish screen that was deposited during the high flows of 2011. Constructed in 2002, the screen prevents fish from becoming trapped in the irrigation canal.
“Despite severe drought conditions this year, the Grand Valley Water Users Association managed to continue operation of the fish screen which minimizes mortality of endangered fishes,” said regions U.S. Fish and Wildlife Service director Steve Guertin. “Operating the screen during periods of extremely low river flow is vitally important, as a larger percentage of the river is being diverted compared to periods of more normal river flows,” he said.
The Palisade Irrigation District took advantage of the low flows to repair extensive damage to the fish passage at Price-Stubb Diversion Dam caused by last year’s extremely high flows. The passage, which became operational in 2008, allows endangered fish to move freely up and down the Colorado River.
On the Gunnison River, the Bureau of Reclamation’s reoperation of the Aspinall Unit (consisting of Blue Mesa, Morrow Point and Crystal dams and reservoirs) for endangered fish enabled the Redlands Water and Power Company to operate its fish passage and fish screen from April through September. As of early August, more than 9,000 fish had used the passage. Of those, 90 percent were native fish including 10 endangered Colorado pikeminnow.
“After two decades of effort by Recovery Program partners to construct these fish screens, fish passages and water management facilities, it was gratifying to see all water users working together collaboratively to minimize the impacts of the extreme drought conditions,” said Brent Uilenberg, technical services division manager for Reclamation’s Western Colorado Area Office.