Vail Valley streams getting warmer, affecting the trout |

Vail Valley streams getting warmer, affecting the trout

We could see some relief — rain — by the end of this week, thanks to monsoonal flows

This warm, dry summer is causing rising stream temperatures, and sluggish fish. If you're going out, hit the river early in the morning.
Scott Yorko/courtesy
Is the monsoon coming? The National Weather Service’s Grand Junction office is predicting that monsoonal moisture could hit eastern Utah and western Colorado as soon as the middle of this week. The moisture is badly needed, but forecasters say slow-moving storms could produce for flash flooding, especially in areas that have seen recent wildfires.

We may be in the dog days of summer, but trout also slow down in the heat.

Colorado Parks and Wildlife over the weekend warned that streams around the state are getting warm enough to affect fish, particularly trout.

The release states that when water temperatures exceed 70 degrees, trout “often stop feeding and become more susceptible to disease.”

Warm temperatures and low water levels can also lead to the creation of algae blooms in streams and reservoirs. That can cause water oxygen levels to drop when those algae die and decompose.

Local fishing guides keep close track of water temperatures and other conditions, and are adjusting their trips accordingly.

Head out in the morning

“We’re scheduling all our trips in the morning — it’s just too warm to fish in the afternoon,” Eagle River Anglers owner Bob Nock said.

Nock noted that trout get sluggish enough in warm water that fishing during the heat of day is essentially “a waste of time.”

And, Nock added, if someone does hook a trout in the middle of the day, that fish is under undue stress when it’s released.

At Fly Fishing Outfitters in Avon, owner John Packer said he’s also encouraging people to fish early in the morning, or after dusk, when temperatures have moderated.

Water temperatures on the Eagle River range into the mid-60s, Packer said. Temperatures above that start affecting both fishing and the fish.

Packer said in addition to warm temperatures, low streamflows are also stressing the trout.

Packer said the upper Colorado River is running about 800 cubic feet per second. The seasonal norm is about 1,200 cubic feet per second. Packer said reservoirs in Grand County are expected to begin water releases this week. That should both boost streamflows and drop temperatures.

Relief on the way?

Streams and the trout could get another boost this week. The National Weather Service is predicting a flow of monsoonal moisture could arrive in the central and southern mountains by the end of this week.

Rain would be helpful, for both water supplies and to moderate water temperatures. While slow-moving storms could lead to flash flooding in spots — particularly on scars from recent wildfires — streams, fish and humans could all use a respite from what’s been a warm, dry spring and summer.

The U.S. Drought Monitor’s most recent report shows almost all of Colorado is in some stage of drought. Eagle County is about split from “abnormally dry” to “moderate drought.” Almost all of the southern part of the state is in the “extreme drought” category.

Until the rains come, fishing guides are sticking to before-noon times. Some guide companies also hold permits to lead trips at higher elevations when temperatures are cooler.

And, Packer said, there’s been plenty of demand for gear and trips.

“We’re crazy-busy,” Packer said, adding that people who fish, especially with flies, “invented social distancing hundreds of years ago… People who have never fly-fished have taken it up this year.”

Vail Daily Business Editor Scott Miller can be reached at

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