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Watch your genitalia — Pacu fish on the hunt for nuts

Experts say there is no cause for alarm. We advise all swimmers to keep their shorts if swimming in the Øresund

It’s 20 cm long, has large, human-like teeth, and eats nuts. Fears of a piranha infestation were raised, as a pacu, a close relative of the piranha, was caught in Øresund. Experts warn swimmers to watch their testicles, as the pacu fish can mistake them for food.

A pacu fish, normally native to South America, was caught in eel-traps by Einar Lindgreen, an ameteur fisherman, according to a press release by the Natural History Museum. As the 21.5cm long fish was flopping, exposing its big teeth and red underbelly, concerns were raised that it was a piranha, and thus a danger to swimmers. This is fortunately not the case, as fish experts Peter Rask Møller and Henrik Carl from the Natural History Museum examined the specimen and concluded that the fish was a close relative to the piranha, called the pacu.

The usual suspects

The pacu can grow to be much larger than the piranha, weighing up to 25 kilograms, and is omnivorous. Its natural habitat is South America, so how it ended up in Danish waters remains a bit of a mystery.

The usual suspects are fish farmers and aquarists, according to Peter Rask Møller, as quoted by the Natural History museum. It is quite possible someone emptied their pacu fish tank into the stream, trying to dispose of the unwanted fish, who managed to survive.

The Blue Planet aquarium, which is near Øresund, is also a potential culprit, although Lars Skou Olsen, head of the aquarium, dismisses this possibility.

Keep your shorts on!

“We have pacu fish exhibited in our aquarium, but they are much larger, and although there are only a few meters between our fish and the fish found in Øresund, there are watertight bulkheads and sophisticated filter systems in between. So it is not one of ours that is out!”, he says to the Natural History museum.

Only one specimen of the pacu fish has been caught in Europe before. In 2002, this fish was captured in the Odra river in Poland, according to Peter Rask Møller.

In general, while pacu fish are related to Piranhas, they are not aggressive, and would not attack swimmers, as they largely feed on carasses of other fish, as well as any fruit and nuts which may be floating in the river. It is their affinity for nuts that should give one pause, however, as there have been reports of pacu fish mistaking testicles for nuts in Papua New Guinea. As it is impossible to rule out whether there are more pacu fish in the water, the University Post must encourage all readers to keep their shorts on while swimming in Øresund.

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