Danish swimmers escape waters fearing killer fish

Aug 12, 2013
Pacu teeth. Credit: Henrik Carl

The capture in the Danish/Swedish strait of Oresund of a fish some twenty centimeters in size and with long sharp teeth has caused Danish swimmers to leave the water fearing an invasion of meat eating killer fish, Piranhas.

There is however no cause for panic say experts. The fish, though exotic, is a Pacu, not a piranha. None the less they caution male swimmers to protect their privates when swimming in the sound.

"Discovering whether this fish is a lone wanderer or a new will be very exciting. And a bit scary. It's the first time this species has been caught in the wild in Scandinavia," says Associate Professor and fish expert Peter Rask Møller of the National History Museum of Denmark, University of Copenhagen.

Caught by hobby fisherman

The frightening fish was caught by hobby fisherman Einar Lindgreen on August 4. As he emptied his nets north of Danish isle Saltholm in the strait Oresund which seperates Denmark and Sweden he saw the red-bellied bigtooth among eels and perch. Back in the harbour the exotic fish caused quite an uproar, as several of Lindgreens colleagues were convinced that they were staring at a South American Piranha. Fortunately the fish was sent for study at the Natural History Museum of Denmark. Here Peter Rask Møller and fellow fish expert Henrik Carl examined the animal. Their calming communique for Danish bathers is that the fish is not a Piranha but a close South American relative; the Pacu.

Though the Pacu, like its cousin the Piranha, belongs in waters like the Amazon it has found its way to other waters around the globe by way of aquariums and fish farms. In large parts of the USA and Asia it is now considered an invasive species. It grows to as much as 25 kilograms and is a popular fish for farming and eating. But how this fish ended up in Scandinavian waters is a bit of a puzzler.

Pacu. Credit: Henrik Carl

Some have imagined that it escaped from the recently established The Blue Planet - Denmark's Aquarium. This Copenhagen attraction is situated right next to Oresund and gets its water from there.

But that is flat out impossible assures curator at The Blue Planet Lars Skou Olsen.

"We do exhibit Pacus in our Amazonas exhibition, but ours are a lot larger than the one caught. And even though the distance between our aquariums and Øresund can be measured in meters there are sophisticated filters in place to avoid contamination. So this is not one of our fish," assures Olsen.

The usual suspects

"Amateur aquarium owners and fish farmers are "The usual suspects" when we meet fish where they do not belong," says Peter Rask Møller.

"It is not unlikely that someone has emptied their fish tank into a nearby stream just before a vacation and that the Pacu then swam out into the brackish waters of Oresund. We don't know of any commercial farming of Pacus in Europe. But just like the Piranhas the Pacus are quite easy for amateurs to raise," says Møller.

Danish boy Malthe with Pacu. Credit: Henrik Carl

Only once before has a Pacu been caught anywhere in Europe. That was in 2002, when a sportsfisher hooked one near a power plant on the Odra river in Poland.

"The river Odra empties into the Baltic Sea very close to Denmark," says Peter Rask Møller.

The Pacu is known as the peaceful cousin of the Piranha as it is largely vegetarian. Their powerful teeth are not as sharp as those of the Piranhas, but they are fully capable of severing fishing lines and even fingers.

"In order to be one hundred percent certain of the identification we will now perform a genetic examination, as there are several species of Pacu which are very similar when young. In the aqua culture busines they even produce hybrids between species," explains Peter Rask Møller.

The teeth are used mainly to crush nuts and other fruits, but the Pacu eats and small invertebrates as well. Its preference for nuts have had fatal results though. In Papua New Guinea where the species has also escaped it is rumoured to have mistaken nuts for male reproductive organs. So anyone choosing to bathe in the Øresund these days had best keep their swimsuits well tied.

Explore further: Tiny new catfish species found in Rio Paraiba do Sul basin, Brazil

add to favorites email to friend print save as pdf

Related Stories

'Dead or alive' bounty offered for China piranhas

Jul 12, 2012

Authorities in southern China have moved to quash a bizarre piranha threat, offering bounties and free bait amid fears the aggressive South American fish has invaded a river, state media said on Thursday.

New DNA-method tracks fish and whales in seawater

Aug 30, 2012

Danish researchers at University of Copenhagen lead the way for future monitoring of marine biodiversity and resources. By using DNA traces in seawater samples to keep track of fish and whales in the oceans. A half litre ...

Blue-bellied fish is a surprise catch

Mar 28, 2013

It is only 7mm longer than the world's smallest fish, and seems to only appear at night, but the bright blue belly of a tiny Amazonian fish caught the eye of a team of scientists who spotted it was a new ...

Recommended for you

Plants with dormant seeds give rise to more species

Apr 18, 2014

Seeds that sprout as soon as they're planted may be good news for a garden. But wild plants need to be more careful. In the wild, a plant whose seeds sprouted at the first warm spell or rainy day would risk disaster. More ...

Scientists tether lionfish to Cayman reefs

Apr 18, 2014

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

PhyOrgSux
3 / 5 (6) Aug 12, 2013
Papua New Guinea where the species has also escaped it is rumoured to have mistaken nuts for male reproductive organs.


should probably be:

Papua New Guinea where the species has also escaped it is rumoured to have mistaken male reproductive organs for nuts.
Torbjorn_Larsson_OM
5 / 5 (2) Aug 12, 2013
Well, nuts!
rug
2 / 5 (4) Aug 12, 2013
Ouch!

More news stories

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.