An Amazonian fish related to piranhas was found in Petaluma Pond in San Francisco, leaving researchers baffled how the animal got there. Members of this fearsome-looking species exhibit teeth resembling those found in human beings.

A pacu fish was caught by fisherman Juan Gallo as he was fishing on Lucchesi Park. As the angler raised his catch out of the water, the fish bit into the line holding it to the reel. Gallo was able to prevent the animal from escaping, and he plans to donate the catch to the state Department of Fish and Wildlife.

"It landed on the dirt and you could tell it wasn't anything we had seen before," Gallo said, describing his unusual catch.

The waterway where the fish with the sardonic grin was found normally has a much more mild-mannered reputation, as the location is typically known as a duck pond.

Pacu are freshwater fish, native to the Amazon River. Their heritage ties the animals to the often-terrifying piranhas. The animals are occasionally sold as exotic pets in the United States, although they are illegal in The Golden State.

In 2015, another fisherman caught a pacu fish in Roberts Lake while angling in Rohnert Park. In June of that year, another of the creatures was found in the Swedes Lake in New Jersey.

The pacu has a reputation of eating testicles of male swimmers in the Amazon, adding to its character as a flesh-eater. This notion of an animal born to emasculate men was driven by an episode of the television show River Monsters, first broadcast on Animal Planet in 2011. A story of two men perishing after having their testes eaten was soon picked up by tabloids in the United Kingdom, and the tale became popular on the internet.

"The bleeding was so severe that they died. The locals told me that this thing was like a human in the water, biting at the testicles of fishermen. They didn't know what it was. It is a hot and dirty area so the people would often go to the water with their children to wash but obviously they were very worried about this thing in the water,"Jeremy Wade, who hunts the fish, said.

Despite their reputation, pacu usually only eat plants and small fish.

If state officials don't want the invasive animal, Gallo told the press he may have the creature stuffed.

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