Mola mola (ocean sunfish) are the world’s heaviest bony fish reaching weights up to 2,268 kilograms (5,000 pounds See Giant Sunfish Below). With their huge, flat bodies, truncated tails, tiny mouths and big eyes, they have been described by the Monterey Bay Aquarium as looking "like the invention of a mad scientist.”
The Mola mola was originally described in 1758 as Tetraodon mola by Carl Linnaeus, the founder of modern taxonomy, in his book, Systema Naturae 10th edition. Mola is the Latin word for millstone — a reference to these fish’s roundish shape.. Mola mola bodies are often covered by parasites. One scientist counted 50 different types on one sunfish. Sometimes mola mola come to the surface and float on their sides so that gulls can fly down and remove fish-lice from their sides.
There are a number of interesting names exist for ocean sunfishes around the world including: 1) Manbo (Japanese); 2) Schwimmender kopf (German), meaning “swimming head”; 3) Poisson lune (French), meaning “moon fish”; 4) fān chē yú (Chinese), meaning "toppled wheel fish"; 5) Putol (Philippines), Bisaya dialect for “cut short”; 6) Samogłów, (Polish), meaning "head alone" or "only head"; 7) klumpfisk (Swedish, Danish and Norwegian), meaning "lump fish". [Source: oceansunfish.org; Wikipedia]
Mola Mola spend a lot of time near the surface of the water. When their fins pierce the surface they are sometimes mistaken for shark fins. In May 2023, National Oceanic and Atmospheric Administration Office of National (NOAA) wildlife officials spotted fins n the waters off the California coast and first thought they belonged to sharks. In a photo posted on Facebook, the animal can be seen with its head and backfin poking out of the water, “impersonating a shark in Greater Farallones National Marine Sanctuary,” according to the NOAA Marine Sanctuaries posts. “Duunnn dun… duunnn dun… wait a second, that’s no shark – it’s a mola mola,” the agency said. “These odd creatures get their name" sunfish "from their habit of laying their bodies on the surface of the water to warm themselves by the sun. These ocean giants roam the seas in search of their favorite food, jellyfish.” [Source: Daniella Segura, Sacramento Bee, May 20, 2023]
In 2016, researchers from China National Genebank and A*STAR Singapore, including Nobel laureate Sydney Brenner, sequenced the genome of the mola mola and found several genes which might explain the fish’s fast growth rate and large body size.. Analysis of the genome data suggests that sunfish and pufferfishes diverged approximately 68 million years ago, a finding corroborated by other recent studies based on smaller datasets.
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se; Encyclopedia of Life eol.org; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures
Moladie — the Mola Family
Mola mola belong to the Molidae family and mola genus of fish. Some sources recognize five species within the Molidae family: 1) the common mola, Mola mola (first described by Linnaeus 1758); 2) giant ocean sunfish, Mola alexandrini (first described by Ranzani in 1839); 3) the hoodwinker sunfish, Mola tecta (Nyegaard et al. 2017); 3) the sharptail sunfish, Masturus lanceolatus (Lienard 1840); and 5) the slender sunfish, Ranzania laevis (Pennant 1776). The ocean sunfish are in the genus Mola, currently composed of three species: Mola mola, Mola alexandrini, Mola tecta. [Source: oceansunfish.org]
Most sources recognize three species in the genus Mola: Mola mola, Mola alexandrini, Mola tecta. The common name “sunfish” is used to describe the marine family, Molidae, as well as the freshwater family, Centrarchidae. The common names “ocean sunfish” and “mola” refer only to the family Molidae and can be applied all Molidae species. The name “ocean sunfish” comes from their habit of lying atop the surface of the ocean appearing to sunbathe.
All species of sunfishes are found in tropical and temperate marine waters. Recent tagging studies have finally debunked once and for all the characterization of sunfishes as passive drifters. Tagged specimens indicate that sunfishes have high-energy burst swimming capabilities and can reach speeds of 21.6 kilometers per hour (13.4 mph, 6 m/s), and can swim long distances against major currents. Their cruising speed is only around 3.2 km/h (5 mph).
Giant Mola Mola The giant sunfish (Mola alexandrini) is the largest member of the Molidae family and is larger than the mola mola. It is also known as the bumphead sunfish, Ramsay's sunfish, southern sunfish, southern ocean sunfish, short sunfish or bump-head sunfish. It is closely related to the more widely known Mola mola, and is found mostly in the Southern Hemisphere — although a dead found near the Azores in 2021 weighing in at 2744 kilograms (6049 pounds) — by far the largest bony fish every found (See Below). [Source: Wikipedia]
The giant sunfish has a relatively small mouth and its teeth fused into a parrot-like beak. Their bodies are flat and round, with large fins that they swish back and forth to propel themselves with as they swim horizontally. Their skin has rough denticles, leathery texture, with brown and gray coloring with pale blotches until death when they turn white. The body has a thick white subcutaneous gelatinous layer that is smooth to the touch with a laterally compressed body covered in small rectangular scales.
In December 2017, a convincing case was that the giant sunfish may be a senior synonym of Mola ramsayi based on both historically and newly published morphological data. In July 2020, building upon this scientific learning, the larval forms of these species were discovered for the first time and confirmed with DNA analyses by Australian and New Zealander scientific teams.
Mola Mola Habitat and Where They Are Found
Mola mola are one species of Molidae. They live in saltwater or marine environments and are usually found in the open ocean far from land. They are native to the Indian Ocean, Atlantic Ocean and Pacific and Mediterranean Sea. Mola Mola are thought to migrate to higher latitudes during the spring and summer months to pursue their migrating zooplankton prey. [Source: Brandon Griffin, Animal Diversity Web (ADW) /=]
Adult Mola mola are found in temperate and tropical oceans across the globe. They prefer the open ocean but occasionally venture into kelp beds and deep coral reefs in order to be cleaned of parasites by fishes such as wrasses and Emperor Angelfish. Sunfish are most often found in water warmer than 10 °C (50 °F); prolonged periods spent in water at temperatures of 12 °C (54 °F) or lower can lead to disorientation and eventual death./=\
Mola mola are frequently observed off the coast of Southern California, Indonesia, the British Isles, the Northern and Southern Isles of New Zealand, the southern coasts of Africa, and in the Mediterranean and occasionally in the North Sea. There are places off Japan and Bali where scuba divers seek them out. Most sightings in the British Isles and North Sea occur during the summer, particularly in June and July, when the waters are between 13̊ and 17̊C (55̊ to 63̊F).
Mola Mola Size and Lifespan
mola mola on the surface Mola Mola have a large body and are the largest bony fish, reaching lengths of over three meters (10 feet) and a height of 4.26 meters (13 feet). Ones have found weighing over two tons — 2235 kilograms (4923 pounds). Typically adults weigh between 247 and 1,000 kilograms (545 and 2,205 pounds).
Mola mola grow fast. One weighed 26.3 kilograms (58 pounds) when it was brought to Monterey Bay Aquarium in the 1980s. After being fed shrimp and fish for 15 month it ballooned to 400 kilograms 880 pounds. According to Guinness Book of Records in the 1970s the heaviest bony fish ever recorded was 14-foot, 4,927-pound Mola Mola which was accidently struck by the “ SS Fiona” and carried to Port Jackson Harbor near
A giant sunfish weighing over 2,721 kilograms (6,000 pounds) was found off Portugal's Azores archipelago in December 2021 (See Below). Before that the largest bony fish recorded anywhere near that size was a female mola of the same species caught in Japan in 1996 that weighed around 2,300 kilograms (5,070 pounds) and measured roughly 8.9 feet across.∑
The lifespan of Mola Mola is currently unknown. A member of the same family, sharptail mola are estimated to have a lifespan of 82 to 105 years.[Source: Brandon Griffin, Animal Diversity Web (ADW) /=]
Really Big Giant Sunfish Mola Mola — the Biggest Bony Fish Ever
In December 2021, a dead thre-meter (10-foot) -long giant sunfish found floating just off the coast of Faial Island in Portugal’s Azores archipelago in the mid-Atlantic Ocean weighed over three tons — 2744 kilograms (6049 pounds), the weight of a Chevrolet Suburban — making it by far the largest bony fish every found. [Source: Annie Roth, New York Times, October 19, 2022]
Annie Roth wrote in the New York Times: More than 90 percent of fish have bony skeletons and thus fall into the category of bony fish. This sets them apart from sharks, rays and some fish that have cartilaginous skeletons. Although no bony fish has ever come close to reaching the size of a whale shark, the largest cartilaginous fish, the size of the sunfish found in the Azores is impressive. “It’s pretty rare to find big fish these days due to overfishing and habitat degradation,” said Kory Evans, a fish ecologist at Rice University who was not involved in the discovery of the SUV-size sunfish.
Mola mola The Mola mola (ocean sunfish) and its relatives are largest of all true fishes and the heaviest of all bony fish. Found in all the tropical and temperate oceans of the world, they look like giant fish heads flattened by steamrollers and is propelled by a couple of fins. They are related to puffer fish. Mola mola is their scientific name.
The massive southern sunfish found in the Azores is “not an abnormal individual whose extreme size is due to a genetic mutation,” said José Nuno Gomes-Pereira, a marine biologist with Atlantic Naturalist and co-author of a study published this month in Journal of Fish Biology that documented the specimen. “This species can get to this size. We just finally managed to weigh and measure one. There are more of these monsters out there.”
After local fishermen and boaters found the southern sunfish floating near the Azores, a group of scientists from the research nonprofit Atlantic Naturalist and the local marine wildlife authorities towed its body into Horta Harbor and hoisted it onto land using a forklift. Gomes-Pereira and his colleagues spent several hours measuring the length, weight and stomach contents of the fish. The mola’s nearly 8-inch thick skin made the dissection particularly tricky. And because the fish was too large for any local museum to preserve, it was buried on a nearby hillside.
The scientists weren’t able to determine the exact age of the fish, but Gomes-Pereira believes the creature was at least two decades old. Estimates suggest that is around the limit of their life span, but no one really knows how long these animals can live. This particular fish’s life may have been cut short. While examining the fish, Gomes-Pereira noticed a large contusion on the side of the animal’s head. That could be a sign that the fish was hit by a boat.
Mola Mola Physical Characteristics
Mola Mola are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature) and have bilateral symmetry (both sides of the animal are the same). [Source: Brandon Griffin, Animal Diversity Web (ADW); Wikipedia /=]
Mola mola have a large body that is compressed and ovular. They are scale-less, and have a thick, rubbery skin and irregular patches of tubercles over their body. Unlike other most other bony fish, Mola Mola do not have a caudal (tail) fin or caudal peduncle (the tapered region behind the dorsal and anal fins where the tail fin attaches to the body). They instead have a clavus, which is a truncated tail, used more like a rudder than for propulsion. The clavus reaches from the rear edge of the dorsal fin to the rear edge of the anal fin. The dorsal and anal fins of Mola Mola are tall, and their small pectoral fins point toward the dorsal fin . The dorsal fin has 15 to 18 soft rays, and the anal fin has 14 to 17 soft rays.
Mola Mola also have small mouths with fused teeth that form a beak-like structure, which prevents them from being able to fully close their mouths. They also have pharyngeal teeth in their throat. Mola mola don’t have a swim bladder, which most other fish have. Some sources indicate the internal organs contain the neurotoxin, tetrodotoxin, which pufferfish (fugu) are famous for having. Others dispute this claim.
Mola mola vary in coloration, though the head, back, tips of the anal and dorsal fins, and clavus are generally a mixture of dark grey-brown and dark silvery grey. They have a white belly and sometimes have white splotches on their fins and dorsal side. Adult ocean fish do not possess a lateral line, and only one gill opening is visible on each side, which is located near the base of the pectoral fins. /=\
The spinal column of Mola mola contains fewer vertebrae and is shorter in relation to its body than that of any other fish. Although the sunfish descended from bony ancestors, its skeleton contains largely cartilaginous tissues, which are lighter than bone, allowing it to grow to sizes impossible for other bony fishes.
Mola Mola Behavior
Mola Mola are generally solitary, although they are found in groups when being cleaned by other fish. Little is known regarding the home range of Mola Mola or their methods of communication and perception. They sense using touch and chemicals usually detected with smell. /=\
Mola Mola are often seen basking on its side occasionally near the surface, which is thought to be used to re-heat themselves after diving in cold water for prey, recharge their oxygen stores, and attract gulls to free them of parasites.
But contrary to the belief that sunfish spend much of their time basking at the surface, Mola. mola adults actually spend a large portion of their lives actively hunting at depths greater than 200 meters (660 feet), occupying both the epipelagic and mesopelagic zones.
Mola Mola Behavior and Very Slow Swimming
A research team led by Yuki Watanabe, an associate professor of marine zoology at the National Institute of Polar Research, compared the long-distance cruising speeds of 46 species of fish in a paper published in April 2016 on the Proceedings of the U.S. National Academy of Sciences. Sunfish and salmon were the slowest: An 87-kilogram sunfish swam at 2.2 kilometers per hour (kph) (1.4 miles per hour (mph)) and a 3.3-kilogram salmon at 2.7 kph (1.7). A 428-kilogram great white shark swam the fastest at 8.1 kilometers per hour (kph (5 miles per hour (mph)), followed by a 240-kilogram bluefin tuna at 7.2 kph (3.5 mph). The scientists used small monitoring systems attached to fish. [Source: Earth.com, January 16, 2017]
Annie Roth wrote in the New York Times: Aside from their size, molas are known for their clumsy swimming style. Unlike most fish, molas use their dorsal and anal fins to propel their huge, hulking bodies through the water, which they do slowly and haphazardly. The open-ocean fish are often seen floating on their sides at the sea’s surface, which scientists think is to warm up or to make it easy for seabirds to make a meal of the parasites on their skin. [Source: Annie Roth, New York Times, October 19, 2022]
Unlike most fish, mola mola swings their dorsal fin and anal fin in a characteristic sculling motion. According to Animal Diversity Web: Mola Mola use their dorsal and anal fins as their primary means of locomotion. They flap these fins in a synchronous motion, which also allows them to swim on their side . They occasionally swim near the surface, exposing their top fin, and may even jump out of the water in an apparent effort to detach parasites. Their protruding dorsal fins are sometimes mistaken for those of sharks.
Mola Mola have been observed repeated diving below the thermocline during the day, possibly to forage for zooplankton that migrate vertically . They may also dive below the thermocline in order to avoid predators. Mola Mola have also been observed basking at the surface of the water on their side, drifting with the ocean current. This may be an attempt to re-warm core body temperature after diving into colder water . [Source: Brandon Griffin, Animal Diversity Web (ADW) /=]
Mola Mola Food, Eating Behavior and Predation
Mola mola are generalist predators that largely consume small fish, fish larvae, squid, and crustaceans and are often seen most often in kelp beds. It was once thought mola mola fed almost exclusively on jellyfish and gelatinous zooplankton, such as ctenophores, salps, and medusae, but studies suggest these creatures make up only 15 percent of a sunfish's diet. Occasionally they will ingest eel grass. This range of food items indicates that the sunfish feeds at many levels, from the surface to deep water, and occasionally down to the seafloor in some areas.
Mola Mola have also been observed eating soft bodied invertebrates, crustaceans, mollusks, seaweed, eel larvae, and even flounder. Mola Mola are thought to migrate to higher latitudes in response to zooplankton migrations during the spring and summer months. They may also migrate vertically during the day to prey upon jellyfish and zooplankton found below the thermocline. . Among the plant foods they eat are macroalgae[Source: Brandon Griffin, Animal Diversity Web (ADW) /=]
The mola mola mouth is like a big sucker. One researcher told National Geographic. “The worst you’ll get from a mola mouth is a big hickey.” They are a keystone species, meaning their presence or absence strongly affects populations of other species in area where they live. /=\
Mola mola in turn are preyed upon by sharks, orcas and sea lions. The later like to feed on juveniles which they gobble down after tearing off their fins and ripping their body into bit-size pieces. Mola mola may dive below the thermocline to avoid predators. Mola Mola are also occasionally hunted by humans. The sheer size and thick skin of adult Mola mola deters many smaller predators, but younger fish are vulnerable to predation by bluefin tuna and mahi mahi.
Mola Mola Mating, Reproduction and Offspring
Mola mola females produce 300 million eggs, each breeding season, making them the most fecund living vertebrate. . Little is known about their breeding behaviors. Off the coast of Japan, spawning is thought to occur between August and October. Theeggs are very small, with an average diameter of 0.13 centimeters. Little is known regarding the parental behavior of mola mola but is pretty safe to say it is minimal
According to Animal Diversity Web: Mola Mola have two larval stages. Larvae in the first tetradon-like stage are round and spines protrude from the edges of their body. They have a well-developed tail and caudal fin. During the second larval stage, the tail is completely absorbed and spines disappear. Larvae generally measure about 0.25 centimeters in length. Juvenile Mola Mola grow at an considerable rate, averaging 0.02 to 0.42 kilograms/day and sometimes reaching 0.82 kilograms/day. [Source: Brandon Griffin, Animal Diversity Web (ADW) /=]
Sunfish fry have large pectoral fins, a tail fin, and body spines not found in adult sunfish. They , resemble miniature pufferfish, their close relatives. Young sunfish school for protection, but this behavior is abandoned as they grow and get bigger.
Little is known about the mating systems of mola mola fish, although they are thought to have paired courtship. Fertilization occurs when sperm and eggs are shed in the water. Sunfish spawn in the outer circulation of temperate Atlantic, Pacific Oceans, and in the Mediterranean Sea. Some individuals are thought to spawn in the Sargasso Sea. Research indicates that spawning during the month of September result in bigger fish. [Source: Wikipedia]
Mola Mola, Humans and Conservation
Mola Mola are utilized by humans for food; body parts are sources of valuable materials but have not been evaluated by the IUCN, US Federal List, or CITES.. They are considered a delicacy in some Asian countries, including Japan, Korea, and Taiwan.. They are also used in traditional Chinese medicines. In the European Union, regulations ban the sale of fish and fishery products derived from the family Molidae.
Mola Mola are often caught as bycatch in commercial fishing nets. They are frequently caught in gillnets. In southern California, Mola Mola compromised 29 percent of the catch in drift gillnet fisheries targeting swordfish. In the Mediterranean between 1992 and 1994, Mola Mola had a bycatch rate of 70 to 93 percent. In South Africa, the bycatch rate of Mola Mola is estimated at 17 percent. /=\
Mola molas are very docile and human injuries from them are rare. Most injuries have occurred from large sunfish leaping out of the water onto boats. In one case, a sunfish landed on a 4-year-old boy when the fish leaped onto the boy's family's boat. Areas where they are commonly found are popular destinations for scuba divers, and sunfish at some locations have reportedly become familiar with divers. They are more of a problem to boaters than to swimmers, as they can pose a hazard to watercraft due to their large size and weight. Collisions with sunfish are common in some parts of the world and can cause damage to the hull of a boat, or to the propellers of larger ships. Such collision also injure and kill many mola mola. [Source: Wikipedia +]
Mola mola are not widely seen in aquariums due to the unique and demanding regime needed to take care of them. Some Asian aquaria display them, particularly in Japan. The Kaiyukan Aquarium in Osaka is one of few aquariums with M. mola on display, where it is reportedly as popular an attraction as the larger whale sharks. They have also been displayed at the Lisbon Oceanarium in Portugal the Valencia Oceanogràfic in Spain and Denmark’s Nordsøen Oceanarium. An ocean sunfish named Kukey, which resided at Kamogawa Sea World in Japan and started captivity in 1982, set a world record for captivity for 2,993 days, living for eight years. Kukey was 72 centimeters (2.36 feet) at the time of delivery, but was 187 centimeters (6.14 feet) in size at the time of death. +
Image Source: Wikimedia Commons, NOAA
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; oceansunfish.org,Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.
Last updated March 2023