Wildlife officials believe someone dumped a handful of the pet fish into Teller Lake a few years ago and now they have multiplied to thousands

This article is more than 5 years old

This article is more than 5 years old

Next time you think of dumping your goldfish rather than cleaning out the bowl – again – think twice. Fish sticks and Aqua Bob Squarepants could threaten the stability of an entire ecosystem.

Goldfish have taken over a lake in Bolder, Colorado, and their spread is threatening to wipe out local species. Park officials are now weighing plans to rid Teller Lake of the brightly coloured pests before they spread into the state’s wider water ways.



Wildlife officials believe someone dumped a handful of the pet fish into Teller Lake a few years ago. That handful has now multiplied to thousands. Outside the confines of a bowl, the fish have grown to several inches long and now threaten local species.



“My biggest concern was the fish would escape downstream,” aquatic biologist Ben Swigle of the Colorado parks and wildlife service told NPR.



He said Colorado had a very short transitional zone between cool, Rocky mountain streams and a more warm-water fishery. “The goldfish are super adaptive and they can live in a variety of environments so they have the potential to compete with other native species and potentially supplant those to a point that they may no longer exist in Colorado,” he said.



Three plans are under consideration:

Electrofishing: stunning the fish with electric prods, scooping them up and giving them to bird sanctuaries.

Using Rotenone, a plant-based chemical that at normal doses kills all gill-breathing animals while leaving mammals, birds and reptiles unaffected.

Draining the lake.



“No matter what type of pet you have, there’s sentimental value but there are better ways of disposing of a unwanted pets than harming a public water,” Swigle said.



What should you do with an unwanted goldfish? If it’s dead Swigle suggested putting it in the freezer overnight then putting it in the trash. “If the fish is alive ... we recommend putting it in the freezer and then disposing of it in the trash.”

