Officials of the Colorado Parks and Wildlife (CPW) have launched an investigation aimed at finding out how thousands of goldfish managed to occupy a local lake in Boulder.

The population of the exotic species, first discovered in Teller Lake #5 on March 13, has reached an estimated 3,000 to 4,000 and has now become a threat to the lake's ecological balance. The presence of the invasive species could disrupt the ecosystem.

One angle that wildlife officials have looked into is that a handful of goldfish may have been dumped into the lake several years ago. The pet fish may have then multiplied to the massive number seen today.

"Goldfish are not a native species and are very harmful to the local aquatic ecosystem," said Kristin Cannon, Boulder's district wildlife manager. "We strongly encourage the public not to dump their unwanted pet fish in our waters. It is bad for our environment as well as illegal."

Jennifer Churchill, spokeswoman for the Colorado Parks and Wildlife, said that this fish population will have to be removed in order to ensure the integrity of Teller Lake. This can be done either by draining the lake and rebuilding the natural fish stock or by bringing in specialized boats that would pick out only the goldfish from the water for electroshocking.

"With electroshocking, you go in the boat and stun the fish to paralyze and collect them," Churchill said. She explained that the process is non-lethal for the goldfish. The collected fish will then be taken to a raptor rehabilitation center where they will be used as feed.

In November 2012, a similar event was observed at Thunderbird Lake in Boulder where about 2,275 nonnative koi goldfish overwhelmed the ecosystem. Wildlife officials used electrofishing to remove the fish, which had been reproducing in the lake for two to three years.

The two incidents have raised questions about the proper handling of nonnative species as household pets.

CPW's senior aquatic biologist Ken Kehmeier pointed out the long-term implications of introducing exotic species of animals into an environment they are not used to.

"Nonnative species can be devastating to native populations by causing disease outbreaks and creating competition [imbalance]," Kehmeier said. "It's an issue that anyone concerned with our environment should know about."

As of the moment, CPW officials have yet to determine a definite timetable to begin their removal of the goldfish.

Photo: Jeremy Keith | Flickr 

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