Affiliations: The ocean sunfish or mola may seem in a class by themselves butthey belong in the same class with all other bony fishes known as Osteichthyes.Here is their pedigree:
Kingdom Animalia, Phylum Chordata, Subphylum Vertebrata , Class Osteichthyes, Order Tetraodontiformes (includes puffer fish, triggerfish, boxfish and porcupine fish) , Family Molidae, Genus Mola , Species mola. (Currently there are 3 recognized species in the family Molidae: Mola mola–common mola, Masturus lanceolatus-sharp-tailed mola and Ranzania laevis–slender mola. Our genetic work has identifiedpotentially two more species, so stay tuned.
Name: The name mola while sounding Hawai’ian, is Latin and means millstone a visual reference to the mola’s round body shape. In other countries mola have a number of names: poisson lune (moon fish) in France; schwimmenderkopf (swimming head) in Germany and Manbo in Japan, to name a few. The common name “sunfish” refers to their habit of lying on the sea surface apparently sunbathing. Tagging studies suggest this behavior is tied to warming their bodies
between repeated dives into cold deep water. Such sunning behavior may alsohelp mola rid themselves of their many parasites since at the surface seabirds can harvest parasites from the mola’sexposed skin and cleaner fish can aggregate under the mola and pick off parasites from below. This is a very usefulservice as mola can host some 40 different genera of parasites–even their parasites can have parasites!
Habitat and Range: Mola are found throughout the tropical and temperate regions of the Atlantic, Pacific and Indian ocean basins–everywhere except in the polar seas. While they may travel into the middle of ocean basins, most observations and tracking studies reveal them to be primarily coastal residents.
Depth: Mola spend most their time in the upper 40-50 m (150-170 ft) of the ocean. During the day, they can repeatedly dive to depths of 100-300 m (300-1000 ft) and can even dive below 600 m (1968 ft) on occasion. During the night theyare typically less active and rest near the surface, exposing them to dangerous encounters with ship traffic.
Size, growth and longevity: Mola are the world’s heaviest bony fish with the current record holder weighing 2300 kg (5,071 lbs) and measuring 2.7 m (8.9 ft) from mouth to tail. This fish was caught off the coast of Kamogawa, Japan in1996. Historic records reveal mola of longer proportions that likely weighed even more. Mola can increase in weight 60million times from larval to adult size making them the vertebrate growth champions of the world. This is equivalent to a human baby growing to the weight equal to six Titanic ships. In captivity, mola can pack on the pounds–one mola held at the Monterey Bay Aquarium gained 364 kg (800 lbs) in only 14 months. Based on length/weight curves, mola can reach full size in 10 years and live more than 20 years.
Diet, Predators and Role in the Ocean: The bulk of the mola diet consists of gelatinous zooplankton like jellies–a food supply that appears to be rising due to rising human impacts on the ocean. Mola are also known to eat squid, fish, larvae,crustaceans, algae, eelgrass and various midwater and seafloor invertebrates. Mola fall prey to sea lions, sharks and killer whales and provide a wealth of eggs and parasites to other fishes and seabirds.
Reproduction: Mola are considered the most fecund fish in the world. One 1.4 m (4.5 ft) long female was estimated to be carrying more than 300 million eggs! Males and females release their eggs and sperm into the water where fertilizationtakes place however no one has ever seen mola spawn in the wild. Based on plankton collections across the globe, severalspawning areas have been identified including ones off Baja, Japan and in the Sargasso Sea. There are likely many more spawning locations yet to be discovered.
Conservation: Mola comprise a significant portion of bycatch in many of the world fisheries including the California andMediterranean drift net swordfish fisheries and South Africa’s horse mackerel fishery. Our work is helping revealbehavior patterns of mola so as to better conserve these magnificent fish and their vital jelly-eating role in our ever-changing ocean.
For more information visit www.oceansunfish.org
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