Hundreds of dead fish at Prospect Lake in Colorado Springs

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COLORADO SPRINGS — Hundreds of dead fish washed up on the shore of Prospect Lake – a month after the city closed down the lake to bodily contact.

A spokesperson for the city told FOX21 the dead fish appearing are the result of a combination of things; including high water temperatures and the effects of toxic blue-green algae, which appeared back in June.

Colorado Parks and Wildlife is encouraging trout anglers statewide to consider fishing early in the day and in higher altitude lakes and streams as hot, dry conditions and reduced water levels may increase stress to trout populations.

When temperatures exceed 70 degrees, they often stop feeding and become more susceptible to disease, according to CPW.

City officials say Prospect Lake is now about 75 degrees.

July 20

“Anglers should monitor water temperatures and end their trout fishing adventures when water temperatures start to approach 70 degrees,” Matt Nicholl, CPW’s Aquatic Section Manager said. “If trout have difficulty recovering after being caught and are acting lethargic, it’s a good decision to call it quits for the day.”

Nicholl said anglers to seek higher elevation streams and lakes for fishing while the temperatures are hot outside.

The City of Colorado Springs is currently getting assistance from Colorado Springs Utilities for water testing.

Results from the most recent test, which drew a water sample on July 7 (results on July 14), returned a mycrocystin level of 78 micrograms per liter. The acceptable recreational level for myrocystin, a toxin produced by cyanobacteria (also known as blue-green algae), is 4 micrograms per liter.


The increased bacteria levels harm water quality and decrease the amount of oxygen available to animals living in the water, and can produce a toxin that is harmful to humans and pets, according to the Colorado Department of Public Health & Environment.

During the closure, the following activities are prohibited: swimming, bathing, paddle boarding, tubing, water skiing and non-motorized boating of any kind. No pets are allowed. The use of permitted motorized boats is encouraged as this activity can help aerate the water. Fishing areas will remain open, though anglers are urged to clean fish well and remove guts.

The lake is being treated with an enzyme-based, non-pesticide treatment that consumes the biomass at the bottom of the lake and helps oxygenate the water.

Blue-green algae caused a 12-week closure of Prospect Lake in 2019.

>>Click here for an FAQ on blue-green algae from the health department.

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