One of the main reasons divers visit the Nusa islands is to see the mysterious Mola, also commonly known as the Ocean Sunfish. The Mola is native to tropical and temperate waters. The Mola is seen in high frequency, here in the Nusa Penida Marine Park, between the months of July and October. During the months from July to October, the water temperature around Nusa Lembongan, Ceningan & Penida drops. This is due to the colder deeper waters from the Southern Ocean pushing up into the Indonesian Seas. It is possible to see the Mola outside of these months but it is rare.
The mysterious Mola is a unique fish. It is the largest bony fish in the World. The heaviest specimen on record was caught off Kamogawa, Chiba, Japan, in 1996; It weighed 2,300 kilograms (5,070 pounds) and measured length 2.72 metres (8 feet 11 inches). The Mola has a flattened oval disk shaped body. The Mola’s spinal column contains fewer vertebrae and is shorter in relation to the body than that of any other fish. The extended dorsal and anal fins produce propulsion in a sculling like action to drive the enormous body. The Mola does not have a caudal (tail) fin but instead has a Clauvus which acts like a rudder.
The genus Mola belongs to the Molidae family. There are three species of Mola; Mola alexandrini, Mola mola and Mola tecta. Mola alexandrini is the Mola that is most frequently seen in the waters around the Nusa islands. It’s distinguishing features are; it has a spotty colouration with a scalloped shaped clauvus. The Mola mola has a hug head and chin bump. Mola tecta, also known as the ‘hoodwinker’ mola, as it was recently discovered in 2017, can be identified by the slit on it’s clauvus. Mola tecta has a slight bump on it’s head and chin. Molas also have bumps behind the pectoral fin, these bumps look different on each species, but you need to put under a microscope to tell them apart. The other members of the Molidae family are the ocean sunfish; Masturus lanceolatus, also known as the ‘Sharpetail’ mola as it possesses a sharp tail projecting from it’s clauvus. Ranzania laevis, the ‘Slender’ sunfish, is the smallest and arguably the most beautiful. It has the most colourful, smoothest and thinnest skin of all the members of the Molidae family.
The most common Mola behaviours observed in the local marine park is both the Mola cleaning and rewarming behaviours. There are many Mola cleaning stations around the Nusa Penida Marine Park. The most famous cleaning stations are found at Crystal Bay, Blue Corner and SD (Sekolah Dasar) dives sites. This is where the Molas come to be cleaned by the reef fish. Up to 54 species of parasites may reside on the skin of the Mola and internally. The bannerfish, emporer angelfish and butterfly fish clean the Mola. This is a symbiotic relationship; the Mola gets cleaned and the reef fish get feed. If the water temperature is cold and you see bannerfish, emporer angelfish and butterfly fish schooling together just off the reef, there is a high probability that you can see a Mola. Seagulls also clean the Molas. The Seagulls eat the larger copepod type parasites on the Mola’s body. As the Mola lay on it’s side on the surface of the water, the seagull can rest on the Mola’s body and pick at the parasites.
Another behaviour displayed by the Mola is their rewarming behaviour. Mola’s can dive to depths of over 600 meters. The water temperature at these depths can be icy cold. Prolonged periods spent in water at temperatures of 12 °C (54 °F) or lower can lead to disorientation and eventual death. The Mola is believed to thermoregulate. The Mola lays on their side on the water’s surface soaking up the Sun’s rays on their large surface area or stay in shallower warmer waters after less deep dives. Interestingly, sunfish are able to warm their bodies so effectively that scientists suspect there are underlying adaptations we have yet to discover. This is further supported by the fact that large sunfish lose heat slower than small ones.
The LDC team hope that you have found our blog article interesting and informative. If you would like to find out further information about the Mola or diving in the local area, please do not hesitate to contact us; firstname.lastname@example.org We look forward to your visit to Lembongan Dive Center to come dive with us to see the mysterious Mola. Stay tuned for more information on ‘The Life of the Mola’ to come in the future.