The Ocean Sunfish are the heaviest bony fish on the planet being able to reach weights of over 2,300kg. They can also grow to formidable sizes. One animal that was struck by a boat off Sydney, New South Wales, Australia in September, 1908 measured 3.1m from snout tip to "tail" fin and 4.26m from dorsal fin to anal fin tip. Mola mola held the record as the world's heaviest boney fish, however, recent research revealed that the honour actually belongs to Mola alexandrini - the Bali sunfish. Reference: Sawai et al. (2018)
A 1.37m female was found with approximately 300 million eggs in her ovary, which means that the Ocean Sunfish holds the record for producing the most number of eggs at one time of any vertebrate species. Reference: Schmidt (1921)
From larval stage to adulthood (0.25cm larvae to a 3m adult) they undergo 60 million times an increase in mass. Reference: Gudger (1936) in Pope et al (2010)
A recent study suggests that the main function of this behaviour is to absorb the heat from the sun and surface waters, rejuvinating them for their regular deep, cold dives to forage for food. It has been observed that, while sunfish bask, birds take the opportunity of an easy snack by pecking off the parasites on the sunfish's skin, giving the sunfish the bonus of a good clean. Reference: Nakamura et al (2015)
A tagging study of Ocean Sunfish (Mola mola) in the Northwest Atlantic, recorded a sunfish reaching a maximum depth of 844m. Reference: Potter & Howell (2011) Ocean sunfish exhibit daily vertical movement, visiting deeper depths numerous times during the day, with warm-up breaks in between at or near the surface. At night they tend to remain in shallower waters. Reference: Dewar et al. (2010)
The name 'Sunfish' is thought to refer to the sunbathing habits of these fish. In some countries, however, they are known as 'Moonfish' (Poisson lune in France, Pez luna in Spain, Maanefisk in Norway). In Germany they are efficient in their naming, and call them ‘Swimming Head’ (Schwimmender kopf), and in Denmark they don't beat around the bush and call them "Clump Fish" (klumpfisk). How many more can you find?
The word 'mola' in Latin means 'millstone' so was an appropriate name for this roundish and flattened out fish.
The Sunfish’s outwardly visible teeth are fused together to form a beak-like structure.
The Sunfish has long claw-like teeth in its throat. It eats by sucking water, with food in tow, into its throat and then repeatedly spitting and sucking that water. The food is pushed back and forth over these sharp throat teeth, being shredded up nicely for consumption.
The answer is a resounding yes and no! The sunfish diet has been found to change with sunfish size from food found foraged on the sea floor by small sunfish, to a ‘jelly fish’ diet in larger sunfish. Season may also play a part in the changing dietary habits of sunfish. Reference: Syväranta et al (2012), Nakamura and Sato (2014), Nakamura et al (2015), Sousa et al. (2016)