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Low flows on Dolores River trigger limits on fishing

Anglers being asked to only fish in the morning below McPhee dam
Anglers are asked to avoid fishing on the Dolores River below McPhee dam after noon to avoid stressing trout populations. (The Journal file)

Colorado Parks and Wildlife has requested that anglers do not fish the Dolores River below McPhee Dam after 12 p.m. to avoid further stressing trout suffering from low water and high temperatures.

The voluntary fishing closure is for the section of the Dolores River from McPhee Reservoir to Bradfield Bridge, and is effective June 24.

“The voluntary closure will remain in effect until further notice, with a possibility of an emergency closure to all fishing if conditions worsen,” a Colorado Parks and Wildlife news release said.

The Dolores River is a local favorite tailwater fishery with quality size brown and rainbow trout, said Jim White, Durango area aquatic biologist.

“We know that anglers care deeply about this fishery, and we need their help to conserve this resource,” he said.

The river is flowing at well below historic flows because of the ongoing drought. During years with normal snowpack, flows from McPhee dam are at 70 cfs in the summer or more. But because of low water shortage, flows have averaged 10 cfs in the past few weeks.

A weak winter snowpack, combined with a warm, windy spring, resulted in runoff coming in at 15% of normal 30-year average, according to the Dolores Water Conservancy District.

Fish on the Lower Dolores River below McPhee Dam suffer from low flows because of the drought. Here the river is running at about 10 cubic feet per second. (The Journal file)

Irrigators and the downstream fishery allocation both took drastic cuts as a result of the water shortage.

Increasing water temperature is also a concern for the low flowing Dolores River below the dam, White said.

At times, the river’s temperature has risen to 75 degrees, which is unhealthy for trout, he said.

The temperature of the river is highest from noon throughout the rest of the day. Water cools overnight, so fishing only during morning hours will help to minimize impacts to trout.

Although many trout anglers practice catch and release, in these conditions, it is extremely stressful on fish when they are hooked and handled.

White said fish might look fine when they swim off quickly after they’re released, but they expend a lot of energy when caught, and recovery is difficult in low, warm water.

With less water, there is less habitat available for the fish, and warming temperatures mean less oxygen available in the water. That can lead to increased trout mortality.

“This is the first time we’ve made this kind of voluntary-action request on the Dolores. It’s not something we like to do, but it’s the right thing to do and we hope anglers will join us in this conservation effort,” said John Alves, senior aquatic biologist.

White said the lower flows will shrink the river habitat, and many brown and rainbow trout likely will die this year. The water coming out of the dam is about 42 degrees Fahrenheit, 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.”

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. The fish, listed by CPW as species of concern, have adapted to warm water, but they still need pools and flowing water to survive.

The concern is that lower sections of the river will dry up or be connected only by 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.

Making the problem worse is the smallmouth bass, an invasive non-native fish that thrives in the lower Dolores River but preys on young native fish. Anglers are encouraged to fish for smallmouth bass; they are abundant, fairly easy to catch and have no bag or possession limit.

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

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

jmimiaga@the-journal.com