The ocean sunfish (Mola mola) is a species of sunfish that is found in the euphotic zone in tropical and temperate waters. It gets its name from his habit of floating on its side, at the sea surface, warming itself in the sun. This species has no tail and swims with its very large dorsal and anal fins.
It is the heaviest bony fish in the world, reaching weights of up to 5100 pounds, and the distance from the top of the dorsal to the bottom of the anal fin can be as much as 14 feet.
Ocean sunfish are foraging predators that will eat a variety of food, but their preferred prey are jellyfishes. Jellyfishes are almost exclusively made up of water and are low in calories/nutrients, so a fish with a body as large as the ocean sunfish’s has to eat a whole lot of jellyfishes to support its weight. They have a surprisingly high growth rate and can gain hundreds of pounds in a year, so these jellyfish specialists are always on the hunt. Adults are too large to be threatened by any but the absolute largest potential predators, but medium-sized individuals are eaten by sea lions, killer whales, and large sharks. California sea lions are known to bite the fins off of small ocean sunfish and then play with them like frisbees.
Ocean sunfish are occasionally captured in net fisheries targeting other species. This species has not been assessed by conservationists, but it is likely naturally rare and may be depleted in some areas. Further monitoring of ocean sunfish populations and research into their life history are important to understand this interesting species.