But you may see some coverage of the news playfully (or seriously) suggesting that male sexual organs are at risk whenever these fish are around.
Relax, people with testicles. Relax, everyone. Get back in the water. The pacu may crack nuts with its powerful teeth, but only the edible kind.
The rumor began in 2013, when the fish were spotted in Denmark and a local professor told men to keep their swimming trunks well tied if they ventured into the water. This was a joke, obviously (if you don't get it, just meditate on the word "nut" for awhile), though it's no surprise that people ran with the idea. Since pacu go after fruit and nuts that have fallen into the water, you might think they could confuse certain human parts for dinner.
But they want fresh food, so pacu go after fruits and nuts that they hear plop into the water. That's not really what happens to your body parts when you swim, unless you're really weird about swimming or something.
And to be clear, pacu don't want to nibble on human flesh. They're mostly vegetarian, given the opportunity -- although many pet owners feed them meat, having bought them to serve as a relatively safe alternative to a piranha.
For one final piece of evidence in my pacu-will-not-chomp-on-your-genitals argument: You are a human. Pacu is a fish. You're way bigger than the fish. It doesn't want to get near your hulking, shadowy presence in the water -- even if, for some strange reason, it thinks there might be food right next to you.
It's possible that somewhere, at some point, some human male was bitten by a pacu in an unfortunate location. I failed to find any actual accounts of an attack, but let's face it -- everything with teeth has probably accidentally bitten a human at one point or another. And yes, their teeth are powerful, so a bite would probably hurt, and could even cause damage. But the likelihood of the bite occurring is very, very low.
But it's cool if you want to live in fear of the pacu and its potential dangers. In that care, you're probably wondering how the fish got into a man-made lake in New Jersey, and whether you should expect to run into one at your own local swimming hole. State officials say that the fish are becoming popular pets, and that people dump them in lakes thinking they're doing them a favor.
That's a really bad move for both your beloved pacu and the local ecosystem. Since pacu are tropical fish, they often don't fare well in temperate lakes. And if they do manage to survive, they can upend the local food chain by competing with locals and carrying strange new parasites into the water.