Colorado Parks and Wildlife is requesting anglers refrain from fishing sections of three Southwest Colorado waterways to ease stress on fish caused by warm water temperatures and low water levels.
The voluntary closure from noon to midnight applies to the Animas River through Durango, the Dolores River below McPhee Reservoir and the San Juan River through Pagosa Springs. Temperatures in the rivers have regularly risen above 71 degrees during the past week, according to CPW.
CPW spokesman John Livingston said when fish are put under stress, anglers could find it difficult to catch and release them without causing them harm.
“If you put up a good fight with a fish in the afternoon, right now, while water temperatures are hot, there’s a good chance of stressing that fish out to the point where you can’t safely release it and that fish may die,” he said.
CPW Aquatic Biologist Jim White said the warmer the water gets, the less oxygen it holds.
“So trout being a cold-water organism, they typically need dissolved oxygen in the water at a certain level. And so when the water warms up, it holds less,” he said.
White said fish are exothermic organisms, meaning they don’t regulate their body temperatures, so their body metabolism fluctuates with the temperature of the water. This means if a fish is caught and exerts energy being reeled in, it may not have the proper oxygen to survive in warmer water after being released.
According to a CPW news release, stream flows in local rivers are below 50% of the daily average. Livingston said the low water conditions can cause stress on fish during the hottest parts of the day.
“It just puts pretty tough conditions on fish, especially in the heat of the day, they really just need to kind of sit low in those pools and not having extra added stressors,” he said.
White said low water levels are the major cause for concern, because when there is less water volume, the water is more susceptible to temperature swings throughout the day.
“If there was more water in the Animas River and we had these kinds of hotter temperatures, it wouldn’t probably be as big of an issue,” he said.
CPW advises anglers to fish in the early morning to avoid causing fish greater stress. Livingston said temperatures increase fast in the late morning, so the earlier anglers can start the better.
A Thursday news release said the Animas River has stayed around 65 degrees at night, which means there is not an adequate amount of stress-relief during the nighttime for fish.
Livingston said trout prefer when the water is under 65 degrees. He also suggests anglers fish in the northern parts of the Animas River.
“If you want to fish on the Animas River, we always recommend to go out further north and hit some of the high-elevation creeks or the reservoirs out there if folks want to fish during the afternoons and early evening,” he said.
Recreational tubing can also cause additional stress to fish, according to CPW.
Livingston commends the fishing community in Southwest Colorado for its effort to protect local ecosystems. He said after the 416 Fire in summer 2018, debris contaminated water which led to a large fish die-off in the Animas River, and the community committed to protecting the fish ecosystem. The Animas River is showing signs of recovery as a fishery.
“We’re starting to see some bigger brown trout from our survey work last fall,” he said. “We’ve got sculpins returning to the river and carp returning into the river.”
CPW is having great success and survival rates with rainbow trout that were stocked in the river, he said.
The voluntary closure will remain in effect until conditions improve for fish habitat. For the latest conditions related to mandatory and voluntary fishing closures, visit https://cpw.state.co.us.
tbrown@durangoherald.com
