The Sunfish

The Ocean Sunfish waves its large dorsal and anal fins to move itself, drifting through the open ocean. At almost 10 feet long and 14 feet tall, it is the largest bony fish on the planet.

Common Name
Scientific Name
Diet
Size
Depth
Ecosystem/Habitat
Zone
Ocean Sunfish
Mola mola
Sunfish eat small fish, squid, jellyfish and crustaceans.
11 feet (3.3 m)
2,600 feet (800 m)
Temperate and tropical oceans, often basking near the surface.
Mesopelagic Zone

The Sunfish

Drifting slow through the open ocean, the Sunfish waves its large dorsal and anal fins to move itself. At almost 10 feet long and 14 feet tall, this is the largest bony fish on the planet, and yet it only appears like half a fish. Nicknamed ‘the swimming head’, their peculiar morphology of a curved, truncated shape forms as their back fin never grows; it folds within itself as the fish develops, creating a rounded rudder called a clavus, which the fish uses to steer through the water.

Its appearance is also the inspiration for its latin name, with mola meaning ‘millstone’, due to the sunfish’s circular shape and stone-like skin. Their rough texture is caused by the tendency of this species to become highly infested with skin parasites. This explains some of the peculiarities of its behaviour, as often they are seen breaching the surface up to 10 feet, and splashing back down to shake off the parasites. In a similar fashion to many sharks and turtles, the sunfish allows smaller fish to pick at the parasites on its skin; a symbiotic relationship, in which both organisms benefit. Being such slow-moving creatures, they feed on creatures that drift with the ocean currents. This includes jellyfish, plankton and algae, which they engulf in their small, beaked mouths that are unable to close completely.

The Mola mola truly are a beautiful species, and yet like all marine life they are threatened by human activity. With many suffocating on plastic which they mistake for jellyfish, or getting snagged in nets as they are clumsy swimmers, they are classified as vulnerable. This is evidence for the important role of marine conservation in preserving unique and threatened species like the sunfish.

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