Fish in streams and rivers across Southwest Colorado are likely stressed as water levels dwindle.
Low flows and high temperatures lead to lower dissolved oxygen levels in the water, which can be tough on fish facing many summer stress factors, said John Alves, senior aquatic biologist for Colorado Parks and Wildlife’s southwest region.
“There are a lot of stressors out there between anglers, rafters and tubers,” he said.
Anglers should consider fishing in streams and rivers during the morning when water temperatures are cooler and not during the heat of the day, he said. In the afternoons, area lakes, such as Nighthorse, Haviland, Pastorius and Lemon, offer good alternatives, he said.
Fighting a fishing line when oxygen levels are low could be deadly for a fish, even if it swims off after being released.
“There could be no effect. There could be delayed mortality,” Alves said.
CPW closed a section of the Yampa River last month to protect an excellent fishery during low flows, and biologists are monitoring streams and rivers across the region for similar conditions that would be lethal to fish, he said.
Alves could not predict whether area rivers and streams might see a fish die-off.
Fish in the Animas River near Farmington, where stream flows are about 5 cubic feet per second, are likely to travel upstream or downstream into deeper water, he said.
They could travel upstream into colder water or downstream into the San Juan River, where the flows are more reliable, he said.
The monsoon could increase river and stream flows, but the runoff is also likely to bring more ash and sediment into the Animas River from the 416 Fire burn scar.
“The ash is the first punch delivered after a fire,” he said.
With low stream flows and warm temperatures Colorado Parks and Wild
Silt follows the ash down into rivers and creeks, and it covers up the invertebrates that the fish feed on and clog their gills, Alves said.
The local chapter of Trout Unlimited recently advised its members of the tough conditions and made suggestions similar to those recommended by CPW.
“We have to be sensitive to the resource, and I think everybody is doing what they can,” said Buck Skillen, conservation chairman for the Five Rivers Chapter of Trout Unlimited.