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Courtesy of Marcus Rosten

How This Little Goldfish Can Cause Big Trouble

In 2017, Marcus Rosten pulled a goldfish the size of a small dog from the Niagara River in New York. But it wasn’t the first time a monster goldfish had been caught in the U.S.

Goldfish living in a bowl in your family room are harmless. But goldfish in U.S. waterways are an invasive species. That’s an animal or a plant that moves into an area and harms native species. Tens of millions of goldfish have invaded bodies of water across the country.

From Pets to Pests

Goldfish are a type of carp that is native to Asia. They were first brought to the U.S. more than 200 years ago. By 1900, goldfish were being given away as carnival prizes. Today, they are as common in U.S. homes as cats or dogs.

But what happens when people decide they no longer want their goldfish? Often, they think the most humane way to part with a pet fish is to release it into a pond or stream. But they might actually be creating a gigantic problem.

“Besides being illegal to release goldfish into the wild, it’s irresponsible,” explains Sarah Muskopf. She’s an aquatic biologist with the U.S. Forest Service.

A Struggle to Survive

Goldfish swimming in a fishbowl eat only a few flakes or pellets of food each day. But fish released into rivers and lakes have access to an almost unlimited supply of plants, insects, and smaller fish to eat.

With no natural predators to keep them in check, these eating machines can grow to be more than a foot long. And they multiply quickly. Female goldfish lay up to 40,000 eggs per year. All those unwelcome goldfish end up competing with native fish for food.

“Because invasive goldfish are larger and more plentiful, they usually win,” says Muskopf.

The way goldfish search for food can also be harmful. They are bottom-feeders, meaning they find food along the floor of a body of water. That stirs up sand and mud, making the water murky. Native fish struggle to survive in those conditions, and the entire ecosystem is affected.

What You Can Do

Goldfish have been spotted in bodies of water from Alaska to Florida. Often, there are so many in a lake or river that it’s impossible to get rid of them all.

The best thing people can do, Muskopf says, is to stop dumping their pet fish. People should bring unwanted goldfish to a pet store or an aquarium.

After all, a photo of a giant goldfish might make a great viral tweet, but is it worth it?

1. Why are goldfish considered invasive species?

2. Do you think it is humane or irresponsible to release goldfish into the wild? Support your response with evidence.

3. How are goldfish similar to Burmese pythons? Use details from the article and sidebar to support your response.

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