A South American fish feared because of attacking testicles has been found in the southern coast leading experts to warn Swedish men not to take off their swimming trunks if going out for a swim.

The warning came last week after a Oresund Sound fisherman caught a 2.1-centimeter long pacu – a relative of piranha that is most usually swimming around the Amazon region.

The fish is known to have a habit of attacking the human testicles which made the freshwater fish “pacu” dubbed as “ball-cutter.” This fish can grow bigger than a piranha, reaching up to 25 kg (55 pounds) in weight and 0.9 m (3 feet).

Though found mostly in the South America’s Orinoco and Amazon basins, spotting have also been reported in a number of U.S. States and in Papua New Guinea where introduction of pacu fish is believed to boost fish stocks.

As reported by the Telegraph, a fish expert from a museum confirmed that this is the first time a pacu has been sighted and captured in Europe.

Henrik Carl, a fish expert at the Danish museum claimed that Pacu fish are not usually harmful to people but has quite a bite, a serious bite. He cited an incident in Papua New Guinea, where some men are believed to have had their testicles munched by pacu fish.

The pacu looks closely similar to their dangerous relative piranha, that when looking from the outside, you can’t even determine which is which. However, they have a little dissimilarity, their set of jaw alignment; pacu have squarer, straighter teeth like a human, whereas piranhas have piercing, sharp-edged teeth.

The sighting of one pacu should not keep men having fun in the water. But it will be another case if more will be caught, said Carl.

He concluded, "This one was the first, but who knows, it's probably not the last."