" One of the most fearsome predators freshwater has ever known, the Tigerfish has a viscious reputation. These fish hunt in large packs, just as their South American counterparts, the Piranhas do. Prey consist primarily of other fish, but just about anything alive can fall prey to the Tigerfish. Like the Piranha, prey is eaten away bite by bite. Because they have razor sharp knife-like teeth, and extremely strong jaw muscles, they are among the few fish that can turn the tables on prey the same size or larger than themselves. There are unverified reports of attacks on humans."
more at : http://lordsofapathy.blogspot.com/2007/04/animal-spotlight-goliath-tigerfish.html