Which fish is the heaviest living bony fish?

The ocean sunfish is the heaviest living bony fish.

Its scientific name is Mola mola, and it belongs to the family Molidae. Unlike sharks and rays, which have skeletons made largely of cartilage, ocean sunfish have bony skeletons. Adults commonly weigh hundreds of kilograms, while exceptionally large individuals can exceed 2,000 kilograms.

Ocean sunfish have a distinctive flattened, oval body and unusually short-looking rear fins. Their apparent tail is a rounded structure called a clavus, formed from modified fin rays. They feed on jellyfish and other soft-bodied animals, although their diet can also include squid, crustaceans and small fish.

The ocean sunfish is sometimes confused with the southern sunfish, another very large mola species. “Heaviest bony fish” refers to body mass, not length: some elongated bony fish may be longer, but no living bony fish matches the ocean sunfish’s maximum weight. They occur in temperate and tropical oceans worldwide and are often seen basking near the surface.