Bumphead sunfish, Ramsay's sunfish, Southern sunfish, Southern ocean sunfish, Short sunfish, Bump-head sunfish
The giant sunfish or bumphead sunfish (Mola alexandrini), (also known as the Ramsay's sunfish, southern sunfish, southern ocean sunfish, short sunfish or bump-head sunfish in various parts of the world), is a fish belonging to the family Molidae. It is closely related to the more widely known Mola mola, and is found in the Southern Hemisphere. With a specimen found dead near the Azores in 2021 weighing in at 2744 kg (6049 lb) it is the largest extant bony fish species in terms of maximum recorded mass by a wide margin. It can be found 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.
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withMola alexandrini has a relatively small mouth, and its teeth are fused into a parrot-like beak. It can reach up to 3.3 m (11 ft) in length and 2,700 kilograms (6,000 lb) in mass, making it the heaviest bony fish. 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 and a leathery texture, with brown and gray coloring with pale blotches; at death, their scales 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. Both mola species have no caudal bones, ribs, or pelvic fins, and have fused vertebrae, leaving only their median fins to propel themselves. Mola alexandrini can be distinguished from Mola mola by its smaller number of ossicles and lack of a vertical band of denticles at its base. In Mola, the lower jaws are intact while the upper jaws are slightly forked. On the head, the lateral lines have small, white, rounded otoconia. On the sides are small gill openings covered by a soft gill membrane and gill rakers, which are covered under a subcutaneous gelatinous layer. All fins are spineless and triangular. Pectoral fins are small and rounded, located midlaterally fitting into shallow grooves on sides of the bod, and dorsal fins are located on both sides of the anal fin.
M. alexandrini can be distinguished by its unique characteristics of head bump, a chin bump, rectangular body scales, and rounded clavus. Although adult sunfish look generally similar, they are distinguishable using seven characteristics: number of clavus fin rays, number of clavus ossicles, shape of clavus margin, presence of head bump, proportion of body length compared to body height, shape of body scales, and the presence of a chin bump.
Alongside these species, there are no external differences between sexes; internally, however, the gonads differ in shape, with females having a single spherical ovary and males having a pair of elongated, rod-like testes.
Overall, the maximum recorded weight of M. alexandrini is 2,744 kg (6049 lb) from a 325-cm-length (10.66 ft) specimen caught off the coast of Faial Island, Azores, Portugal in late 2021. With these records, this specimen is currently regarded as the world's heaviest bony fish specimen. It exceeds by nearly half a ton (444 kg, 979 lb) the largest previously known specimen (2300 kg, 5070 lb), caught off Kamogawa, Japan in 1996.
Mola alexandrini has been found all over the globe and is widely distributed throughout the world's oceans, except for the polar regions. These species have been collected from waters off Japan, Taiwan, the Galapagos Islands, New Zealand, Australia, Turkey, Oman, and Spain. It can be found in the southwest Pacific, especially around Australia and New Zealand, and the southeast Pacific around Chile. Its range also extends to the southeast Atlantic near South Africa. During seasonal changes in climate on the Pacific side of Japan, M. alexandrini moves northwards in the summer and southwards in the winter. Seasonal migration is driven by temperature differences and productive frontal areas.
Although members of the genus Mola are found in many oceans throughout the world, this species thrives best in the open ocean of tropical and temperate seas, preferring warmer temperatures ranging from 16.8 C to 25.6 C (62.24 F to 78.08 F), averaging 19.9 C (67.82 F) . Many encounters with this species are linked to the influence of ocean currents. Based on their immediate environment, sunfish have different movement patterns. During the nighttime, these species stay in the same areas, but during the daytime, they stay below the thermocline. Vertical movement patterns correlated with thermocline depth, and they differed from December to May.
Sunfish swim by moving their dorsal and anal fins back and forth, both fins moving in the same direction at the same time. Adults are reported to travel mainly alone or in pairs, and sometimes in groups. Migrating from one place to another requires high tolerance and it is found that sunfish have high thermal tolerance undergoing quick and large temperature changes diving down the ocean several hundred meters. Sometimes, sunfish come up to the shallow water to recover from hypoxia from feeding below the thermocline. Like many other fish, sunfish adapt in response to the environment. During the day, sunfish tend to dive deeper than they do at night. During the nighttime, sunfish preferred temperatures between 18–24 C (64–75 F) while the fish moved to different areas during the day. Vertical movements were correlated with temperature shifts. Sunfish may dive deeper into cooler waters to cool the muscles or to repay oxygen debts.
Just like many other fish, high mortality rates are common for eggs, larvae, pre-juveniles, and small juveniles due to predators. There have been few reports on predation of Mola species however, predation by fish are from families Scombridae, Carangidae, Coryphaenidae, Xiphiidae, and Alepisauridae. Although there is not much research on the lifespan of ocean sunfish, ocean sunfish reportedly take about 20 years to reach a length of 3 m (9.84 ft).
They mainly consume jellyfish, which are of low nutritional content but abundant, and they will also eat brittle stars, small fish, plankton, algae, salps, and mollusks. Sunfish also feed on ctenophores, hydrozoans, and small crustaceans. Juvenile sunfish feed in coastal areas in the coastal food web while larger sunfish dive deeper. These species are active predators hunting in dynamic frontal systems.
Sunfish spawn in the outer circulation of the temperate Atlantic and Pacific Oceans, as well as in the Mediterranean Sea. The optimal time for sunfish to spawn in the wild is not known, but research has shown that spawning in fall or winter, especially during the month of September, results in bigger fish. Fertilization occurs when sperm and eggs are shed in the water. Being that sunfish are so large, a single adult female can produce 300 million eggs. Unfertilized eggs were measured at 0.42-0.45 mm in diameter.
The conservation status of M. alexandrini has not been evaluated, unlike M. mola. Fisheries around the world catch ocean sunfish as bycatch. M. mola was listed by the International Union for the Conservation of Nature (IUCN) as "vulnerable" due to the high level of estimated bycatch in South African longline fishery with an annual estimated 340,000 annual catches. Both M. mola and M. alexandrini were listed as "high risk" bycatch species in the longline fishery off eastern Australia. Threat levels are lower than what is stated on the IUCN listing in Australian, New Zealand, and South African fisheries. Currently, the Indonesian government's Ministry of Marine Affairs and Fisheries has placed sunfish on a plan for protection.
The importance of ocean sunfish in marine food webs is unknown. However, since ocean sunfish feed on gelatinous prey with a generalist diet, this suggests that these species play an important role in coastal food webs. If sunfish were to be removed as bycatch, it can drive localized trophic cascades with top-down control being reduced.
Sunfish have economic value in tourism industries. These fish make unpredictable appearances, but when they do appear, it is often a moment of excitement for tours and scuba divers. In locations like the Galapagos Islands and the Alboran Coast in the Mediterranean, sunfish are spotted frequent enough to have sunfish tours. Scuba diving tourism in Bali and the Nusa Penida islands has rapidly increased over the last few decades. Only a small number of fisheries target sunfish, including those in Taiwan and Japan. In Indonesia, sunfish are released, eaten by locals, used as bait, or end up at a fish market on rare occasions.
