A testicle-eating fish that's native to South America has shown up in a pond in Russia, The Moscow Times reported.

Pacu, a relative of the piranha, were spotted by a fisherman last week in an enclave known as Kaliningrad located in the Baltic. The fisherman caught several of the exotic fish and took them to marine biologists who later identified the species.

Pacus normally feed on algae and tree nuts. But every now and then they are known to mistake the male genitals for the tree nuts, attacking men who swim in the waters of South America.

"[The pacu's] mouth is not so big, so of course it normally eats nuts, fruit and small fish, but human testicles are just a natural target," Henrik Carl, a museum expert, told NPR according to Fox News. "It's not normal to get your testicles bitten off, of course, but it can happen."

There have been multiple sightings of the pacu, nicknamed the "ball cutter," in other parts of the world. Two men in Papua New Guinea were reportedly killed after being attacked by a pacu in 2011.

Last summer, the tropical fish was found swimming in the Oresund Sound between Denmark and Sweden. In September, pacus were found swimming less than 20 miles outside New York City.

Another was caught earlier this month by a Michigan woman fishing in a lake near Detroit, Fox News reported. Wildlife officials told the station someone most likely released it into the lake.

Pacus, which are edible, are popular among aquarium fish and can grow up to 90 centimeters. Experts said the Russian pacu was most likely released by its owner because it was too big, according to The Moscow Times.

Though the fish made its way to the Russian pond, it most likely would not have survived the harsh Baltic winter, the newspaper reported.