Known as the heaviest bony fish in the entire world, the ocean sunfish or commonly known as Mola has earned some bad reputations for being the weirdest looking ocean creature. However, this animal has so many unique characteristics which include sunbathing! Also known as Mola mola, ocean sunfish appeared between 45 and 35 million years ago, after the dinosaurs disappeared and at a time when whales still had legs. Mola comes from a Latin word which means millstone that refers to the fish’s disc-like physique. It also carries different name as another reference to its shape: moonfish. In other countries, i.e., Dutch, its common name is maanvis, in Portuguese its peixe lua, Poisson lune in French, and pez luna in Spanish. In Germany, this strange looking animal is known as Schwimmender Kopf or swimming head, while in Polish, it is called samoglow, meaning head alone or only head as they believe it has no true tail. It is called sunfish as this animal loves sunbathing at the surface of the water and looks like dead fish lying on their sides, sometimes flapping their dorsal fin. This sunbathing is common activities for them after diving in the deepest parts of the ocean to hunt for prey. It is to reheat the body after diving deep in the water. Sadly, ocean sunfish are prone to infestation by parasites, thus other reason for sunbathing is to attract seabirds from above or fish from below to clean their skin of parasites. This solitary animal can also be found in groups when being cleaned by other fish. Ocean sunfish has rough texture and rounded body with a sparkle gray color. Its distinctive figure is literally at their head as it resembles a fish head with a tail and its main body is flattened. This largest teleost in the ocean has small mouth with a beak-like tooth plate in each jaw with pointed pharyngeal teeth to chomp on jellyfishes. When its dorsal and ventral fins extended, ocean sunfish will be highly tall due to the long-shape body.
Molas can be found in the temperate and tropical regions of Mediterranean, Atlantic, India and Pacific Oceans. They often been caught during the summer months like June and July where the water temperatures are between 13°C and 17°C. They are migrating to higher latitude during the spring and summer months to feed on migrating zooplankton. Their movement is unique as it has no common tail. As they are lacking in tail, they depend on the powerful dorsal and anal fins for agile propulsion. They flap their fins in a synchronous motion to allows them to swim on their side. They even jump out of the water in an apparent effort to detach parasites. They have been found diving below the thermocline during the day to avoid predators. This dependable animal might dive up to 2600 feet and usually hang out at 160 to 650 feet depths. Sunfish is a predator that feds on small fishes, larvae, squids, and crustaceans. Nearly over 1/7 of Mola mola’s diet is basically sea jellies and salps, once thought to be the primary pray of this gigantic animal. They are considered as strategic top-down control of jellyfish population which can influence the direct occurrence of jellyfish blooms. Mola juveniles have always been caught by California sea lions in Monterey Bay. Their natural predators are those top ocean hunters such as sea lions, killer whales, and sharks. Sunfish have quite similarities with pufferfish, porcupinefish and filefish that comes from the order Tetradontiformes.
They can grow up to 10 feet long with 5,000 pounds. They are exactly heavier than SUV car! The body shape of this largest bony fish is compressed ovular which can reach 3.1 m in length and 4.26 m in height. They are scale-less, have thick and rubbery skin with irregular patches of tubercles over their body. They have white belly and sometimes with white splotches on their fins and dorsal side. Female Molas are known to be bigger than males. Females’ can produce more eggs compared to any other known vertebrate like hagfish, lampreys, cartilaginous and bony fish. They can lay up to 300 million at a time. Ocean sunfish is in the Guinness Book of World Records for having the most eggs. It is believed that they have multiple spawners as oocytes in the ovaries was developed in different stages. Ocean sunfish development consists of two larval stages. The most important part is the first tetradon-like stage where the larvae are round, and spines protrude from the edges of their body. During this moment, they have well-developed tail. Later, the second larval stage bring the tail completely absorbed which make the spines disappear. Larvae size is only 0.25cm in length and grown at a logical rate, average 0.02 to 0.42 kg/day. There are limited resources regarding the reproduction of ocean sunfish, but best believed that they have paired courtship. Some individuals are certain spawning in the Sargasso Sea. Their eggs are very small, with an average diameter of 0.13 cm. Research found in Japan that the spawning activity is thought to occur between August and October. Their growth rate, lifespan, reproductivity remains undetermined and mystery.
In the meantime, ocean sunfish is considered a delicacy in some other parts of countries including Japan, Korea, and Taiwan. In European countries, the government has banned the sale of fish and fishery products which derived from the family Molidae as they often been caught in gillnets. The bizarre fact of the ocean sunfish is that they have been used as payment for taxes by Japanese shoguns. In addition, they also used in Chinese medicine and contain the same toxin as puffers and porcupine fish. There is no known shelf life of the ocean sunfish, yet a member of the same family, sharp-tail mola have a lifespan of 82 to 105 years. It is difficult to captive this animal in an aquarium as it has high demanding requirements for care. Molas are something of a star at the Monterey Bay Aquarium, the only facility in North America which exhibiting the bizarre looking fish. For instance, the Kaiyukun Aquarium in Osaka, the Lisbon Oceanarium in Portugal, and Denmark Nordsoen Oceanarium have exhibiting the interesting animal to the public which gain more attractions than sharks. In Kamogawa Sea World, an ocean sunfish named Kukey, started captivity in 1982, holds a world record of 2,993 days living for eight years with 187cm in size at the time of death.
In Southern California, 29% of the catch belongs to ocean sunfish when targeting swordfish. Ocean sunfish are considered vulnerable like cheetahs, polar bears, and giant pandas. They are friendly to humans and not many consider them a delicacy, hence the biggest threats are due to boat hit or being caught in fishing gear. Most of this creature is shy yet can be frequently seen swimming with divers in some locations.