[5] 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 itself after diving in cold water for prey, recharge its oxygen stores, and attract gulls to free itself of parasites.

[12][13] Camillo Ranzani named Mola alexandrini in honour of his contemporary Antonio Alessandrini, a teacher of comparative anatomy and veterinary science at the University of Bologna.

Their skin has rough denticles and a leathery texture, with brown and gray coloring with pale blotches; at death, their scales turn white.

[6] 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.

[6] These species have been collected from waters off Japan, Taiwan, the Galapagos Islands, New Zealand, Australia, Turkey, Oman, and Spain.

During seasonal changes in climate on the Pacific side of Japan, M. alexandrini moves northwards in the summer and southwards in the winter.

As they mature, specimens reportedly reach 4000 mm with well-defined features, along with pigmentations of gray, olive, or black with a brown cast.

[27] Sunfish spawn in the outer circulation of the temperate Atlantic and Pacific Oceans, as well as in the Mediterranean Sea.

[27] Just like many other fish, high mortality rates are common for eggs, larvae, pre-juveniles, and small juveniles due to predators.

[25] 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.

With smart tactics, tiger sharks can stalk and ambush their prey and are able to bite through the thick gelatinous dermis.

[29] 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.

In Indonesia, sunfish are released, eaten by locals, used as bait, or end up at a fish market on rare occasions.

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.