DENVER - The Denver Department of Environmental Health believes annual algae die-off is to blame for the deaths of numerous fish in Sloan's Lake.
Denver Parks and Recreation employees noticed a large number of dying fish in the southwest section of the lake Wednesday morning, near Sheridan Boulevard and West 20th Avenue.
The Division of Wildlife and Environmental workers took samples from the lake and were able to determine the water was not toxic; rather the oxygen levels were low.
On Thursday local environmental officials said dying algae in the lake caused the oxygen levels to drop and kill the fish. A spokesperson with Denver Parks and Recreation said less than a hundred fish died as a result.
The rest of the fish that were concentrated in the southwest area of the lake were dispersed on Thursday when Rocky Mountain Ditch opened the flood inlet allowing more water to flow into the lake. The city said it learned that when oxygen levels are low the fish will go toward the inlet to get to the fresh water coming in, which is what happened on Wednesday.
The next step will be to remove the dead fish from the lake and look at ways to manage algae growth in the future.
The lake will remain closed to fishing until the dead fish are removed. Health workers say the water is safe and does not pose a danger to pets which frequent the park with their owners.