Common Mola - Mola mola
In our New England waters, the most commonly encountered ocean sunfish is the Mola mola, also called the common mola. These extremely large fish can be sighted in Cape Cod Bay and Massachusetts Bay in the summer months of July and August. Common molas are often observed lying on their sides at the water’s surface. They seem to be sunning themselves and this behavior has given them the common name of “sunfish”. Common molas have been observed in both temperate and tropical waters. Yet their exact distribution and overall movements is not well understood.
Common Names: ocean sunfish, round tailed or common mola
The unusual swimming behavior of the common mola often alerts us to the presence of this
animal at the water’s surface. As the fish lies on its side, the dorsal fin flops up and downcausing the water to splash. This sculling motion can be used to help distinguish the common mola from the basking shark. The basking shark also has a large dorsal fin, but the fin is typically observed erect as it moves slowly along the water’s surface.
The common mola has an unusual body shape as well as unique external features. The body is somewhat flat and rounded giving this fish the appearance of being “allhead” and very little tail. This circular, thin body shape is the basis for the Family name, Molidae, which is derived from the Latin word for “millstone”. The skin is silver in coloration and has a slight sheen overall. Although not obvious from a distance, the skin is covered with copious amounts of mucus. The skin is also very thick and has a gritty texture when touched. The animal’s mouth is quite diminished in size and very rounded in appearance. The mouth is formed by the fusion of the animal’s 4 teeth and is used to capture gelatinous organisms, like jellyfish, ctenophores and Portuguese man-o-war.
But don’t let this animal’s strange shape and unusual features fool you. Common molas are the heaviest bony fish in the world, reaching lengths of 6 to 10 feet and weights of 2 to 4 tons. However, little is known about their feeding habits and reproduction. Females have been reported to carry the most eggs of any vertebrate. These eggs are minute in size and when they hatch, produce a larvae that is quite comical in appearance. The larvae of the common mola have numerous spines projecting from many directions. As the larvae grow, their spines and the majority of their caudal - tail fin slowly disappears. Finally, we begin to see a fish that more closely resembles the larger adults.
Many people often refer to the common mola as the “ocean sunfish”. However, there are two other species of sunfish in the family Molidae including the sharp-tailed mola Masturus lanceolatus and the slender mola Ranzania laevis. Although neither species is commonly observed offshore, the sharp-tailed mola have been sighted on a number of occasions in the water’s off New England.
Sharp-tailed molas have have a similar appearance to that of the common mola. However, one obvious difference is that sharp-tailed molas have a projection on the caudal - tail fin. This projection provides the basis for their common name. When you sight a mola offshore it is best to photograph the caudal - tail fin in order to verify which species of mola you are observed.
The terminology used to distinguish between the three different species can be a bit confusing. In actuality, the words “ocean sunfish” can be applied to all three species of mola. Therefore, it is best to refer to the more commonly sighted Mola mola as the common mola, not the ocean sunfish.
Ocean sunfish are not fished commercially in the waters of the United States. However, molas are eaten throughout Asia with Taiwan and Japan being the largest markets.
Classification Scheme for the Common Mola - Mola mola
Kingdom – Animalia
Phylum – Chordata
Subphylum - Vertebrata
Class - Osteichthyses - the bony fish
Order – Tetraodoniformes
also includes the trigger fish, boxfish, porcupine fish and puffers
Family – Molidae
Genus – Mola
Species - mola
Scientific Name - Mola mola
Common Names - ocean sunfish, roundtailed or common mola
Be sure to check our resources page for further information on this fish and other animals inhabiting our coastal water and shores.