Men who plan on skinny-dipping in Scandinavia are being warned about the presence of the Pacu fish, which has been known to bite male testicles, sometimes fatally.
And why is that?
Pacu feed by crushing nuts with their powerful jaws and large teeth, and can mistake the male reproductive organs for their favorite snack, CNN reported.
Just how the Pacu, which is indigenous to South America, ended up in Scandinavia is not quite known, says the Natural History Museum of Denmark.
Latest: Do You Support Giving Illegals Citizenship? Vote Here Now
"Amateur aquarium owners and fish farmers are 'the usual suspects' when we meet fish where they do not belong," Peter Rask Moller, of the Denmark museum, told CNN. He said the fish were first found in the Danish/Swedish strait of Oresund.
The Pacu is a cousin to the piranha, but is vegetarian, which would make the fish fairly harmless, according to CNN. The fish's large teeth aren't as sharp as the piranha's but are "fully capable" of severing fishing lines and fingers, the museum's experts told CNN.
They are known to eat smaller fish and have been declared as an invasive species in most parts of the world, according to
ScienceWorldReport.com.
Two men reportedly bled to death in 2011 after a 40-pound Pacu castrated them while they were swimming in a river in Papua, New Guinea, reported
Metro.com.
"When I reeled it in, it had this mouth which was surprisingly human-like, it is almost like they have teeth specially made for crushing," British fisherman Jeremy Wade said after catching what he believed was one of the culprits. "They are like human molars and the fish have powerful jaw muscles. They are very deep bodied and solid like a carp, with strong muscles."
Last year, Pacu caused a scare in Lake Lou Yaeger in Litchfield, Ill., when some visitors believed they were piranha after two were caught by fishermen, according to
KSDK-TV.
Urgent: Should Obamacare be Repealed? Vote Here Now
Fish biologists told the television station that the fish were probably dumped there illegally and it was unlikely they would survive the winters in North America.
Pacu can weigh up to 55 pounds, but because they are natives of South America would struggle to reproduce and find food in the colder months, according to the
Journal-News.
Related story:
Asian Carp Now in Great Lakes Says Study, Threatening $7B Fishing Industry
Lionfish Grow Into Hungry Atlantic Predators After Florida Release