Piranha Identification Guide
How to recognize a piranha and separate it from the closely related pacu.
Read the full Piranha encyclopedia entry →
Piranhas are deep-bodied South American characins known for their sharp teeth. They are frequently confused with the related pacu.
Key identification features
- Deep, laterally compressed (disc-shaped) body.
- A blunt, powerful lower jaw with interlocking, triangular teeth.
- Coloration from silvery to red-bellied depending on species.
- A small adipose fin behind the dorsal fin.
Piranha vs. Pacu
- Piranha teeth are pointed and triangular for shearing; pacu teeth are squared and molar-like.
- Pacu grow much larger and have a less protruding lower jaw.
- Pacu often have a straighter belly profile.
Common species
- Red-bellied Piranha: silvery-grey with a red to orange belly and throat — the classic aquarium and river species.
Where you'll see one
Piranhas live in the rivers and floodplains of South America. A deep, silvery, disc-shaped fish with a jutting lower jaw and triangular teeth is a piranha; squared molar-like teeth point to a pacu instead.
Frequently asked questions
How do I tell a piranha from a pacu?
Piranhas have pointed, triangular shearing teeth and a jutting lower jaw, while pacu have squared, molar-like teeth and grow much larger.
Are all piranhas red-bellied?
No, only some species like the Red-bellied Piranha have a red belly; others are silvery or darker.