Swimmers in Michigan might be in for a nasty surprise if they get on the wrong side of this fish.

The pacu fish, which is closely related to the piranha, have been found in lakes in Michigan. It is thought that pet owners release pacu fish into the wild when they outgrow their aquariums, according to the Michigan Department of Natural Resources.

Pacu Fish
Image source: Wikimedia Commons

Former pet pacu fish released in Michigan

According to the Michigan Department of Natural Resources, there have been three recent Pacu sightings. Two of the reports came from Lake St. Clair and the other came from around Port Huron.

Setting the fish free into the wild “is almost never humane,” said Nick Popoff, manager of the DNR’s Aquatic Species and Regulatory Affairs Unit.

“Pets released from confined, artificial environments are poorly equipped to fend off predators and may be unable to successfully forage for food or find shelter,” Popoff said. “Those that do succeed in the wild can spread exotic diseases to native animals. In the worst-case scenario, released animals can thrive and reproduce, upsetting natural ecosystems to the degree that these former pets become invasive species.”

Large fish closely related to piranha

The pacu fish have human-like teeth and powerful jaws which make them capable of eating fruit, nuts and plants. Once fully grown the fish can reach up to three feet in length and weigh as much as 55 pounds.

Although the fish do not currently breed in the United States, this could soon be different due to climate change. The DNR says that this is another reason why the fish should not be released into the wild.

The fish shot to fame after it was rumored that they could chew on men’s testicles. It was thought that they could confuse the male testicles with nuts, and decide that it was time for a tasty treat.

Testicle-munching myth debunked by scientists

The rumor was given fresh impetus by Professor Peter Rask Moller of the Copenhagen Museum of Natural History, who told swimmers in Denmark and Sweden to keep their swimsuits on following a pacu sighting.

He later went on CNN to clarify his comments.

“Of course, this is half a joke since it is very unlikely that you would actually meet one here and that it would bite you. It’s up to people themselves how careful they want to be. I’ll keep my shorts on, though.”

Pacu fish are an increasingly popular choice for pet owners around the world, and they have been caught in Paris, Scandinavia and Oceania, as well as the United States. Rumor has it that the fish were at least partly responsible for the death of two men in Papua New Guinea. The pair died of blood loss after the fish apparently castrated them, earning pacu fish the moniker “Ball Cutter” among locals.

However Danish scientists moved to dampen the hype, calling the pacu’s apparent taste for testicles “overblown.” Even if they aren’t going to be munching on human genitalia, the pacu fish are reportedly a threat to local fauna.

As a result it is recommended that pet owners “humanely destroy” their unwanted animals, rather than letting them free.

If you are planning on going swimming in Michigan, it might be worth considering that there may be a “Ball Cutter” on the loose. I personally wouldn’t want to take any chances.