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.

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

Image credits: main image: courtesy of Leonard Lovshin, Department of Fisheries and Allied Aquacultures, Auburn University.