Molidae

Molidae is a family of large, pelagic fishes in the order Tetraodontiformes, commonly known as ocean sunfishes. Members of this family are noted for a highly compressed, rounded body shape and a reduced tail, with a clavus forming a rudder-like shield. They are among the heaviest non-cartilaginous fishes and exhibit a distinctive, buoyant lifestyle near the surface.

Taxonomy and species. The family Molidae comprises three extant genera: Mola, Masturus, and Ranzania. Five recognized species are distributed among these genera: Mola mola (ocean sunfish), Mola alexandrini (southern sunfish), Mola tecta (hoodwinker sunfish), Masturus lanceolatus (long-nosed sunfish), and Ranzania laevis (slender sunfish). The taxonomy reflects ongoing research, with some classifications revising species boundaries in recent decades.

Appearance and size. Ocean sunfishes have a circular, laterally flattened body with a prominent clavus at the end of a truncated tail. They lack a true caudal fin and swim mainly by undulating the dorsal and anal fins. They can reach lengths of several meters and weights up to about 2,000 kilograms, making them among the largest bony fishes. Their skin is often marked with patterns of pale and dark areas, and individuals may sport parasitic creatures such as remoras.

Distribution and habitat. Molids are cosmopolitan in temperate and tropical oceans. They inhabit the open water column (pelagic zone) and are frequently observed near the surface, sometimes basking in sunlight, but they can undertake vertical migrations into deeper waters.

Ecology and biology. Their diet consists mainly of gelatinous zooplankton, especially jellyfish, but they may consume small fish and algae. Reproductive biology is not well understood due to the difficulty of observing spawning in the wild. Bycatch in commercial fisheries and plastic debris pose conservation concerns for several species, with IUCN assessments varying by species.