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What Happens When You Dump Your Goldfish in a Lake?

Goldfish are seen as pretty innocuous creatures. After all, they’re reported to have a memory of fewer than 3 seconds, so how dangerous can they really be? Well, it turns out if you find you don’t want to keep your pet goldfish and decide to dump Goldie into a local lake, you’re creating a big problem. Think Sharknado, but with goldfish.

Goldfish: An Invasive Species?

When an organism creates a home in an environment where there are no natural predators it becomes an invasive species. Invasive species are actually really bad for the environment, causing upheaval in the ecosystem as they kill off other important species that the local environment depends on.

A few examples of invasive species include:

  • Goats in Galapagos – Sailors brought goats to Galapagos Islands that they hoped to breed for food, but they destroyed local plants and also endangered the giant tortoises that had lived there for, well, ever.
  • Asian carp in the Great Lakes – These fish were brought into water treatment plants to control algae, but soon made their way to the Great Lakes where they have endangered many local species.
  • New Guinea flatworms – These nasty worms are wiping out populations of snails in Europe, leaving birds without a food source.

Not all invasive species start out as farm animals or work animals, though, some have started as pets. In Australia, for example, cats were brought as pets from Europe. But that has now translated to a population of 20 million feral cats that directly threaten 124 local species. And now there’s a new threat in Australia – goldfish.

The Goldfish Threat

Goldfish are carp that can actually grow quite large if they aren’t kept in small tanks. They can grow up to four pounds, mostly because they will eat everything they can get their little goldfish lips on. When you dump a goldfish in a pond or in the wetlands, it can easily find its way to other bodies of water and from there, the sky is the limit.

Goldfish in the wild aren’t just an issue for Australians, though. In Canada, the government started pleading with people in 2015 to quit dumping their unwanted goldfish in waterways. Goldfish are also wreaking havoc in lakes and ponds in the United States.

In the wild, goldfish are carnivores. They eat the eggs of other native species of fish and introduce new diseases into local fish populations. They also tend to travel along the bottom of lakes and streams, making it more difficult for other fish to eat in the sediment they kick up.

The moral of this story is that goldfish aren’t as innocent as you think. When it’s time for you to part with your goldfish don’t set him free in the wild so he can morph into a giant carp that will destroy the local environment. Instead, see if a pet shop will be interested in finding him a new home or if you want to euthanize them, do it humanely by just putting them in the freezer. It’s a quick death for a goldfish.

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