“They’re Gonna Die”: #Drought Dooms Trout in #Colorado’s #DoloresRiver—and Probably Beyond — Field & Stream #ColoradoRiver #COriver #aridification #ActOnClimate

From Field & Stream (Sage Marshall) (Click through for the photos from Rig to Flip):

“The stream is flowing anywhere between 5 and 9 cfs,” reports Jim White, an aquatic biologist for Colorado Parks and Wildlife (CPW). “Typical flows are around 70 cfs or higher.”

Such low flows are taking a toll on the river’s trout population. The lack of water leads to higher water temperatures, which directly harm cold-water species such as trout.

“We’ve got a temperature logger placed 2 miles below the dam, and we’re starting to see temperatures upwards of 80 degrees in the evenings,” says White. “We’re starting to exceed what’s called the ‘acute temperature threshold’ for trout, meaning they’re gonna die.”

Managers Expect “Total Mortality” in At Least Half of the Tailwater

The CPW manages a 12 mile stretch below McPhee Reservoir as a catch-and-release tailwater trout fishery. Given the conditions, the agency’s plan is to institute a voluntary fishing closure on the area. Regardless, White expects total mortality of the trout population in the lower half of that section, and potentially in part of the upper half as well. He is also concerned about the river’s mottled sculpin, a native cold-water species and favorite trout food, as well as warm-water native fish such as the flannelmouth sucker, the bluehead sucker, and the roundtail chub populations. That’s not to mention the insects, such as mayflies and caddis, that can’t live in high water temps…

There are two main culprits in the Dolores’ plight: agricultural water use and drought. McPhee Reservoir was a man-made project completed in 1985 primarily to store and provide water for agricultural use in the region. The reservoir itself has become a known hotspot for cliff jumping and catching smallmouth bass, but recent drought conditions have put the project’s long-term viability in question. Not only is the tailwater at 5 to 10 percent of its usual flows, but farmers are only receiving similarly meager water allocations.

Before the creation of the dam, spring runoff would provide enough water to replenish deep pools and runs in the stretch of river that is now suffering. The reservoir is expected to reach its lowest level since its inception this summer.

Experts Eye Trouble for Trout Rivers Across the Region

“We’ve been in a drought for almost 20 years,” says White. “Everybody is suffering from dry conditions here on the West Slope of Colorado and region-wide in Utah and Wyoming.”

White adds that climate change is playing a role in creating extended drought conditions “without a doubt.” According to the U.S. Drought Monitor, every state in the Western U.S. is currently experiencing drought conditions.

Here’s the release from Colorado Parks & Wildlife (Joe Lewandowski):

Due to continuing drought conditions, trout fishing in the Dolores River below the McPhee Reservoir dam will be adversely affected this year, said a Colorado Parks and Wildlife aquatic biologist.

Water releases from the dam will probably be under 15 cubic feet per second (cfs) and could possibly drop as low at three cfs, explained Jim White, aquatic biologist for Colorado Parks and Wildlife in Durango. In normal years, the sustained release from the dam is usually about 60 cfs. The section of river, which flows through the Lone Dome State Wildlife area, from below the dam to Bradfield Bridge ─ a distance of about 12 miles ─ is a popular tail-water fishery. Most trout fishing is done within the first six miles.

White said the lower flows will shrink the river habitat and many brown and rainbow trout will likely die. The water coming out of the dam is about 42 degrees, which is an ideal temperature for trout. But with such a low flow the water will warm quickly as it moves downstream.

“This is going to impact the trout fishery,” White said. “I would expect to see about half or more of the trout fishery habitat suffer and lose much of the trout population.”

White suggested that anglers fish early in the day and carry a thermometer to check the water temperature. Fishing should stop when the water hits 70 degrees.

The low flows will also affect native fish that live in the lower reaches of the Dolores River ─ the Flannelmouth Sucker, the Bluehead Sucker and the Roundtail Chub. These fish are listed by CPW as species of concern. The fish are adapted to survive in warm water, but they still need pools and flowing water to survive.

White is concerned about lower sections of the river drying up or being connected by only tiny rivulets of water.

“I’m worried that the natives are going to be stuck in isolated pools throughout most of the year at these flows,” White said.

Exacerbating the problem are Smallmouth Bass, an invasive non-native fish that thrives in the lower Dolores but are predators on the young of the native fish. Anglers are encouraged to fish for Smallmouth Bass; they are abundant, fairly easy to catch, tasty and there are no bag or possession limits.

As drought continues to grip the West, more and more rivers will be facing the same scenario – this year and beyond.

“All of this is a result of three things: low snowpack, dry soil that will absorb run-off and no carry-over water in the reservoir from last year,” White said.