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It happens all the time. People keep fish as pets and, for whatever reason, decide they can no longer take care of them. Some irresponsible owners take the easy way out and dump their fishies in the nearest lake. In one Colorado habitat, this simple act has created a massive Koi goldfish problem.
The goldfish enjoys the status of being one of the first fish to be domesticated. They are freshwater fish and most often found in ornamental lakes or in fish tanks at homes and doctor’s offices around the world. Rarely do they live in the wild, as they were bred to be pets for humans. In Teller Lake (near Boulder), the descendants of a small handful of abandoned koi goldfish have multiplied so rapidly that they filled the lake.
Photo credit: Colorado Parks and Wildlife
Park rangers estimate that only a few goldfish were dumped in this 12-acre lake about 3 years ago. Those initial fish reproduced, and so on. Now the lake is filled with thousands of koi goldfish, which are not natively found anywhere in North America. Public information officer Jennifer Churchill says, “Someone just didn’t want their goldfish anymore. We don’t think there was malice intended, but now we have 4,000 goldfish. And that’s an issue.” This is a remarkable sight to behold, but marine biologists are alarmed.
If these fish escape the lake and head downstream, they would compete with indigenous fish (such as the stonecat, the common shiner, and the brassy minnow) who share the same diet as goldfish (plankton and insects). The goldfish would not only wreak havoc on these fishes’ food source but also their spawning habitat. There’s also a valid concern that these koi goldfish could carry viruses or infectious bacteria. Pets who live in aquariums often carry diseases that can be controlled in hatcheries where testing is rigorous. An entire ecosystem could be destroyed, simply because someone illegally dumped their unwanted pets.
Biologists hope that they can soon solve this problem in one of three ways: (1) Drain the lake; (2) Remove the fish with the help of rotenone, a chemical that would effectively kill them; or (3) Stun the fish with electricity and scoop them out with nets. If option number 3 is used, these koi goldfish will probably be taken to a raptor sanctuary and used as food for hawks and other such birds.
The United States Geological Survey says the problem of nonindigenous fish dumping problem isn’t limited to this lake. Across the United States, over 1000 non-native species have been dumped in lakes, rivers, or streams. Some of these fish even end up in the wild after they’re flushed down the toilet. Sort of like Finding Nemo without the happy ending.