The ocean sunfish, or common mola, Mola mola, native to tropical and temperate waters around the globe, is the heaviest bony fish in the world, with an average weight of 1000 kilograms. It is flattened laterally, giving it a distinctive oval shape: sunfish are relatively narrow across, but can be as tall, counting their dorsal and anal fins, as they are long. Sunfish live on a diet that consists mainly of jellyfish; as this diet is nutritionally poor, they consume large amounts in order to develop and maintain their great bulk.
When molas are swimming at the surface it is common for their fins to be mistaken for those of sharks.
Adult sunfish are vulnerable to few natural predators, but sea lions and orca whales will consume them. Among humans, sunfish are considered a delicacy in some parts of the world, including Japan and Taiwan, but sale of their flesh is banned in the European Union. Sunfish are frequently, though accidentally, caught in gillnets, and are also vulnerable to harm or death from encounters with floating trash, such as plastic bags.
A member of the order Tetraodontiformes, the sunfish has many derived characters and is the type species of its genus.
Many of the sunfish’s various names allude to its unique “flattened†shape. Its specific name, mola, is Latin for “millstoneâ€, which the fish resembles because of its grey color, rough texture, and rounded body. Its common English name, “sunfishâ€, refers to the animals habit of “sunbathing†at the surface of the water. The French- and Spanish-language names, poisson lune and pez luna, both mean “moon fishâ€, in reference to its rounded shape. In German, the fish is known as Schwimmender kopf, or “swimming headâ€, because it has no true tail. It has various obsolete binomial synonyms, and was originally classified in a pufferfish genus, as Tetraodon mola.
Photo source: Mike Johnson, Earth Window