The “Ball Cutter” Fish.

It may looks placid, but the pacu fish packs a mouth full of teeth. Image Credit: Kazakov Maksim/
by Becky Crew
Becky Crew is a Sydney-based science communicator with a love for weird and wonderful animals. From strange behaviours and special adaptations to newly discovered species and the researchers who find them, her topics celebrate how alien yet relatable so many of the creatures that live amongst us can be.
DON’T LET THAT blunt little mouth fool you – the pacu fish (Piaractus brachypomus) isn’t nicknamed the ‘ball-cutter’ for no reason. Closely related to piranhas, this innocuous-looking, red-bellied silver fish harbours a mouth full of great, big, human-looking teeth.
Native to the freshwater rivers and streams of the Amazon and Orinoco basins throughout the Amazon rainforest, the pacu was introduced to the Sepik River of New Guinea in 1995 so it could be fished locally in what was once an unproductive spot.
And they’ve got plenty of room to roam and grow numerous – the Sepik is the island’s longest river, most of it flowing through the Papua New Guinean provinces of Sandaun and East Sepik, and some through the western province of Papua. In 1997, the species was also placed in the Ramu River in northern PNG.
The “ball-cutter” fish
This is not an unusual practice on island countries and territories throughout the Pacific region. Since 1949, more than 25 species of fish have been introduced in PNG alone to provide additional sources of food and income for the locals. But where the pacu is concerned, the introduction hasn’t exactly been smooth sailing.
Not only has the species threatened local populations of fish, but there have been several reports of nasty injuries to local swimmers due to pacu bites.
According to a study by the Australian Centre for International Agricultural Research, “It is nicknamed the ‘ball-cutter’ by the villagers, because on occasions it has bitten off the testicles of bathing men.”
via The pacu a fish with teeth – Australian Geographic.