Thousands of goldfish were spotted in March in Teller Lake #5 off Arapahoe Road in Boulder, Colorado, and biologists are concerned.
Just a handful of the koi goldfish were likely dumped into the Colorado lake a few years ago.
The fish are not native to the lake and don’t occur naturally anywhere in North America, according to fish biologist Ben Swigle with the Colorado Parks and Wildlife.
Based on the size of the fish and past experience, Swigle suspects they are about 3 years old, meaning someone dumped their unwanted aquarium pets into the lake about three years ago.
He thinks they probably came from just a handful of koi released into Teller Lake.