Pacu travel and migrate in schools. This means that they:

If you came face to face with a pacu, what would you do? Never fear—the pacu may look like a big and scary fish, but it's actually quite harmless. Pacu live in the freshwater rivers that run through the subtropical Pantanal region in South America. Pacu have strong teeth that they use to munch on the seeds and nuts that fall into the water from trees along the river.
Pacu travel and migrate in schools. This means that they:
take lots of class trips
travel together in big groups
all grow up to be very, very smart
Schools are big groups of fish. Some fish like to be alone, but others, like pacu, swim together for protection. This way, they have a better chance of survival. Many eyes are better than just two!
Pacu are sometimes confused with:
piranhas
goldfish
guppies
When pacu are young, they look just like their meat-eating and aggressive relatives, piranhas. Because they look alike, predators usually leave the pacu alone.
Pacu poop helps plants grow.
Pacu poop really does help plants grow! Pacu eat nuts and seeds in one spot and poop them out in another. Since pacu eat and swim, they help transport seeds from place to place.
Pacu are sometimes kept in aquariums by fish hobbyists.
Some people even keep pacu as pets. People who raise pet pacu must have big aquariums to house these large and quick-moving fish.
Scientific name: Piaractus mesopotamicus
Size: 1 to 2 feet long (can weigh over 65 pounds)
Habitat: South American freshwater rivers in the Pantanal region
Diet: seeds, fruits, nuts, and tiny river creatures
Characteristics: large silvery body, small scales, and a golden-yellow belly
Significance: overfishing could put pacu on the Endangered Species List