Mola Mola of Nusa Penida: Encounter the Ocean Sunfish
Nusa Penida is a hidden gem renowned for its vibrant marine ecosystem. Among its most extraordinary inhabitants is the Mola Mola, or ocean sunfish, which stands out as one of the most intriguing and elusive creatures. Here’s a deep dive into the world of the Mola Mola and why Nusa Penida is a hotspot for encountering these magnificent fish.
What is the Mola Mola?
Name and Etymology
The term “Mola Mola” originates from the Latin word “mola,” meaning “millstone,” referring to their flat, round shape. They are also known as ocean sunfish due to their behavior of basking in the sun near the ocean surface.
Species of Mola Mola, The Truth about Mola at Nusa Penida
Research has clarified some misconceptions about sunfish species, particularly those found around Nusa Penida.
There are three species of sunfish—Mola mola, Mola tecta and Mola alexandrini (Mola ramsayi).
The study found that Mola ramsayi, previously thought to be a distinct species, is actually the same as Mola alexandrini.
The sunfish species commonly observed at Nusa Penida is now correctly identified as Mola alexandrini.
Mola molas are without a doubt present in Indonesian waters, yet they do not seem to frequent the Bali reefs like Mola ramsayi does; the extensive archive of Bali mola photos collected as part of the Bali ID Catalogue and Sunfish Research project, does not include a single Mola mola!
Size and Physical Characteristics
Size
The Guinness World Records has historically listed Mola mola as the world’s heaviest bony fish. However research reveals that the heaviest specimens recorded are actually Mola alexandrini, not Mola mola.
This means that Mola alexandrini holds the record for the largest bony fish ever caught.
The record-breaking sunfish, measured 10.66 feet (3.25 meters) in length and 11.78 feet (3.59 meters) in height, weighing 2,744 kilograms.
One of the most distinctive features of Mola Sunfish is its flattened, disc-like body shape. Unlike most fish, Molas lack a traditional tail. Instead, their tail is replaced by a structure known as a “clavus,” which is a rounded, rudder-like projection. This unique adaptation helps them maintain buoyancy and navigate the ocean’s currents. Additionally, Molas have large dorsal and anal fins that extend vertically and assist in their maneuvering through the water.
Mola alexandrini species is distinguished by its large forehead bump, chin bump, and a differently shaped tail compared to other sunfish species. Mola alexandrini has unique patterns on its body, which allow for individual identification. These unique features set it apart from Mola mola and Mola tecta.
Brain Size and Intelligence
Brain Size
Mola Sunfish have relatively small brains compared to their body size. Despite their small brain size, they exhibit behaviors that suggest a certain level of intelligence, particularly in their interactions with other species and their navigation of complex environments.
Ocean sunfish are generally solitary. While not much is known about the specific cognitive abilities of Molas, they demonstrate complex behaviors such as migration, foraging, and interactions with cleaner fish. Their ability to engage in these activities suggests they possess a level of problem-solving skills and environmental awareness.
Diet
Diet
Mola Sunfish species primarily feed on jellyfish and other gelatinous zooplankton like salps and comb jellies. They are considered strategic to control jellyfish populations.
Jellyfish have low nutritional value, therefore Molas need to supplement their diet with higher value food sources. Molas will spend around 50% of their day foraging.
Sunbasking
Despite their large size, Molas have a low metabolic rate and can tolerate a range of temperatures.
It is well known for the Ocean Sunfish to spend up considerable time of the day basking in the sun near the surface of the water; a behavior aiming at re-warming their bodies up after deep water dives to hunt. Another hypothesis for sun basking behavior is parasite elimination.
Migration and Behavior
Migration Patterns
Molas are migratory and travel significant distances in search of food. They often move from deeper waters to shallower regions depending on the season and prey availability.
Seasonal Presence at Nusa Penida
Mola ramsayi is most frequently observed around Nusa Penida between July and October.
They prefer cooler waters, which is why they are often found in areas with upwellings of nutrient-rich cold water. The waters around Nusa Penida offer these conditions, making it a suitable habitat for these fish.
Depth and Distribution
Ocean sunfish have been recorded at a maximum depth of 844 meters, though they typically spend most of their time in the top 50 meters of the water column. They occasionally dive to depths of 400–600 meters, often spending more time at greater depths during the day and returning to shallower waters at night.
A 2015 survey conducted by researchers from Udayana University, Conservation International, and Oceans Initiative off Bali’s southern coast estimated the ocean sunfish population to be around 204 individuals in a survey region of 1,393 square kilometers. This translates to a mean density of approximately 1 individual per 6.8 square kilometers.
Reproduction and Life stages
Prolific Reproduction
One of the most striking facts about the Mola Sunfish is its extraordinary reproductive capacity. A single female can produce up to 300 million eggs at once, making it one of the most fecund vertebrates in the animal kingdom. This remarkable reproductive ability is an adaptation to the many threats Molas face from predators and environmental challenges.
Mating and Egg Production
Molas engage in spawning in deeper waters, where they release millions of eggs. This high fecundity increases the chances that some eggs will survive to adulthood despite high mortality rates among the young. The enormous number of eggs ensures that, even with high predation and environmental hazards, enough offspring survive to maintain the population.
Larval Development
After fertilization, the eggs develop into larvae, which are highly vulnerable to predation. The smallest larva ever weighed was 3.7 milligrams. It is a 700 million times increase in weight from the tiny larvae to adulthood. Arguably the most extreme size growth of any vertebrate animal. The larvae undergo several stages of development before reaching juvenile and eventually adult stages. Their early life is characterized by rapid growth, which is crucial for surviving the many threats they face in the ocean.
The longevity of ocean sunfish in the wild is still not fully understood, though research suggests they can live up to around 20 years. In captivity, recorded lifespan was around 10 years.
Cleaning Stations and Interactions
Cleaning Behavior
Molas frequently visit cleaning stations where smaller fish and cleaner shrimp remove parasites and dead skin. These cleaning stations are crucial for maintaining the health of Mola Molas, as they help rid the fish of parasites.
Cleaning Fish
The most common cleaner fish seen with the Molas are Longfin Bannerfish and Adult Emperor Anglefish – in fact Bali is the only known location where adult Angelfish exhibit this cleaning behaviour.
These fish are crucial for the cleaning process and are often observed interacting with Molas at Nusa Penida.
Diving with Mola Mola
Diving Experience
Diving with Mola at Nusa Penida is an extraordinary experience. Popular dive sites like Crystal Bay, Manta Point, and Blue Corner offer the best chances of encountering these magnificent fish. Due to their elusive nature and variable sea conditions, sightings are not guaranteed
Elusive Nature
Despite their size, Mola sunfish can be challenging to spot. They often float near the surface or at intermediate depths, making encounters somewhat unpredictable. Their behavior of basking in the sun increases visibility, but their elusive nature ensures that each sighting is a rare and thrilling event.
They are generally curious but non-aggressive. To ensure a positive encounter, maintain a safe distance, avoid sudden movements, and never attempt to touch or scare them. If startled, Mola can swiftly swim away, using quick bursts of speed to escape.
Join Us for an Adventure
During the Mola Mola season, we organize trips to Nusa Penida with the hope of spotting these fascinating creatures. While sightings are not assured, each dive offers a unique opportunity to explore the vibrant underwater world of Nusa Penida.
Embark on a diving adventure with us and experience the excitement of potentially meeting the Mola ramsayi in its natural habitat. Whether you’re an experienced diver or new to the sport, Nusa Penida promises an unforgettable underwater journey.
Book your dive today and embark on an unforgettable journey to discover Mola mola of Nusa Penida with Balingo!
