Yes. Arapaima fish have both scales and fins. Their unusually large, overlapping scales form flexible body armor, while their dorsal, anal, pectoral, pelvic and caudal fins provide propulsion, steering and stability.
What do arapaima scales look like?
Arapaima are covered in very large, heavily mineralized cycloid scales. The scales overlap across the body and create an armor-like exterior. Smithsonian’s National Zoo and Conservation Biology Institute reports that an individual scale can reach about 4 inches (10 centimeters) in length; that figure comes from its undated profile, accessed in 2026.
The scales help protect the fish from predators, including piranhas. The broad plates are hard on the outside but are not simply rigid shields. A hard, mineralized surface is combined with inner layers made from collagen fibrils.
Why the scales are both hard and flexible
A 2014 Acta Biomaterialia study by Yang and colleagues found that successive collagen layers are arranged in different orientations, producing a Bouligand-like laminate. This structure helps a scale resist penetration by predator teeth while allowing it to flex with the fish’s body. The combination is a form of flexible dermal armor rather than a brittle shell.
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What fins does an arapaima have?
Arapaima have the full set of fins expected in a typical fish. Their dorsal and anal fins are positioned toward the rear, and the caudal fin forms the tail. Paired pectoral and pelvic fins sit on the sides and underside of the body.
| Fin | Position and main role |
|---|---|
| Dorsal fin | Runs along the back toward the tail; helps stabilize the fish. |
| Anal fin | Sits on the underside toward the rear; contributes to stability and maneuvering. |
| Pectoral fins | Paired fins on the sides; help with steering, braking and fine control. |
| Pelvic fins | Paired fins on the underside; assist balance and maneuvering. |
| Caudal fin | The rounded tail fin; supplies forward thrust and helps direct movement. |
University of Florida IFAS describes Arapaima gigas as having a homocercal caudal fin and posteriorly placed dorsal and anal fins. The Smithsonian also describes a dorsal fin extending along the back toward the tail.
Which arapaima fish does this describe?
The name most often used in general descriptions is Arapaima gigas, known as pirarucu in Brazil and paiche in Peru and Ecuador. A U.S. Geological Survey species profile’s taxonomy discussion recognizes five species in the genus: A. gigas, A. mapae, A. arapaima, A. agassizii and A. leptosome. The anatomy answer remains the same for the arapaima covered by these sources: they possess scales and fins.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why arapaima anatomy is notable
Arapaima are large freshwater fish from the Amazon Basin and obligate air breathers, but those unusual traits do not mean they lack ordinary fish structures. Their distinctive feature here is the combination of a conventional fin layout with exceptionally large, specialized scales that protect the body without eliminating flexibility.
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