The headline in Live Science sounds like the premise for a bad SyFi channel made-for-cable movie – Testicle-Biting Fish  Invading Denmark.  It turns out that a Danish fisherman caught, what is believed to be, a red-bellied pacu, an omnivorous South American freshwater fish related to the piranha, in the Oresund, the strait between Denmark and Sweden.   The fish have what are described as “uncannily human-looking teeth.”  The fish caught in Denmark was quite small at less than 8 inches (20 cenitmenters) long, but can grow much larger. Some pacu can reach three feet long and weigh as much as 55 pounds.

The fish are also rumoured to bite human testicles, earning it the nickname “ball-cutter.”  Whether there is any truth to this rumor is unclear.   Though widely repeated, at least one expert has dismissed the claim as a myth.  The claim seems to be traceable only as far back as December 2011, when two fisherman in Papua New Guinea are reported to have died from loss of blood after being castrated by something in the water. The report came from Jeremy Wade, a British “extreme” angler, who featured the story on his reality TV show River Monsters, on the Animal Planet cable channel, owned by the Discovery Channel.

Neither Animal Planet nor the Discovery Channel are know for their veracity.  We have posted about two fake documentaries on the Animal Planet, suggesting that mermaids are real.  The Discovery Channel has also received considerable criticism over its most recent fake documentary, Megalodon: The Monster Shark Lives.  This is not to say that Mr. Wade is not necessarily reporting accurately, only that the one might take anything presented on the cable channels in question with the proverbial grain of salt.

The pacu, which were considered to be primarily vegetarian, were introduced to Papua New Guinea roughly 15 years ago.  Because they grow rapidly, they are raised in fish farms around the world.

Pacu are often sold by pet stores as “vegetarian piranhas.”  The pet stores may neglect to warn customers of the size to which the fish may grow. There are reports of a toddler whose finger was severely bitten by a pacu in Edinburgh, Scotland. There are also unconfirmed reports of a pacu in Fort Worth, Texas which bit off the nose of its owner after jumping from a tank.   Pacu have been found in lakes and rivers in at least 30 states within the United States.

The good news for Scandinavian skinny dippers is that as a tropical fish, the pacu is not likely to the winter in the region’s colder waters.  In the mean time, swim suits may be recommended.

Thanks to Phil Leon for contributing to this post.