Carl added that pacu fishes are largely vegetarian and nip away at those in the water only because they are hungry. He said: “They bite because they’re hungry, and testicles sit nicely in their mouth.” While the reason the pacu strayed into European waters remains unknown, it could be put down to a hankering for some exotic international cuisine. Swedish meatballs, anyone? The “ball-cutter” fish is native to the Amazon rainforest’s freshwater rivers, but was introduced to various Papua New Guinean rivers in the 1990s so it could be fished locally. As if the island country needed more dangerous creatures.