Don't be alarmed if you're seeing and smelling dead fish recently in the Denver metro area. Heat and algae blooms are likely to blame.
Jason Clay with Colorado Parks and Wildlife (CPW) shared with Denver7 that low oxygen levels, particularly in the summer, can kill some fish species.
Warming temperatures also drive spikes in harmful algal blooms across waterways, which may be contributing to some of these fish deaths.
According to the Colorado Department of Public Health and Environment (CDPHE), toxic blue-green algae have been recently confirmed in several bodies of water including Prospect Lake in Colorado Springs, Barr Lake in Adams County, Cherry Creek Reservoir in Arapaho County, and Steamboat Lake in Routt County.
The toxic blooms are likely in lakes and slow-moving waters, but not so much in rivers and high country lakes.
"Be algae aware! Toxic algae looks like thick pea soup, spilled paint on the water’s surface, or a thick mat of foam along the shoreline," the CDPHE warned watergoers. "If you suspect toxic algae is present, don’t let kids, pets, or livestock touch or drink the water — when in doubt, stay out."
Meanwhile, southwest anglers have been asked to stop fishing at noon daily on several rivers due to low flows and warm water temperatures dangerously stressing out trout. The voluntary closure, which is set to expire on September 25 or until river conditions improve, includes the following:
- Animas River through Durango from the 32nd Street bridge downstream to Rivera Crossing bridge near Home Depot.
- San Juan River through Pagosa Springs from the intersection of U.S. Highway 160 and Colorado Highway 84 intersection downstream to the Apache Street Bridge.
- Conejos River from Platoro Reservoir downstream to Broyles Bridge.
- Rio Grande from Rio Grande Reservoir downstream to the town of Del Norte.
- South Fork of the Rio Grande from Big Meadows Reservoir downstream to confluence with Rio Grande below the town of South Fork.
CPW also posted signs on Monday for a voluntary fishing closure on the Arkansas River from Lake Pueblo State Park dam to I-25.
ANGLER REMINDER: Due to low oxygen & warm water temps dangerously stressing fish, @COParksWildlife today posted signs of VOLUNTARY CLOSURE of Arkansas River from @LakePuebloSP dam to I-25. Use CPW Fishing Atlas to find cool, high country waters to fish. https://t.co/cX2TjJVkhM pic.twitter.com/hvUgaeMwdl— CPW SE Region (@CPW_SE) August 17, 2020
Editor's Note: Warm weather is hard on fish, particularly trout. Consider moving your fishing plans to higher elevation lakes and mountain streams where water temperatures are typically cooler.