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Fun Facts about Mola Mola Sunfish

[Mola Mola Phylum: Chordata] [Class: Actinopterygii] [Order: Tetraodontiformes] [Family: Molidae]

Their common names include mola mola sunfish, mola molas, and even moonfish. No matter which, this species is one of the most advanced for cranial development and evolutionary diversification.

This guide contains some amazing facts about ocean sunfish (Molidae), including where they still exist today, what they eat, and how these enormous bony fishes reproduce.

Where Do Ocean Sunfish (Mola mola) Live?

It's one of the most wide ranging and extensive fish found anywhere in the "Blue Planet" (excluding the polar seas).

But, the global distribution of ocean sunfish thrives best in the tropical and temperate oceans.

They are found most often in the uppermost layer (epipelagic zone) of these warm water oceans, such as the Bali dive sites in Indonesia.

However, scuba divers see adult molas basking near the surface while the sunfish "thermally recharges" itself (known as thermoregulation).

They are renowned for drifting on their side to get maximum sunlight - especially after making deep dives to feed in abyssal depths, sometimes down to 1,000 metres or more (deeper than 3,500 feet).

Scientists link the seasonal movements of ocean sunfish to water temperature and upwelling currents that deliver nutrient-rich food sources (particularly jellyfishes and squids).

Sightings of the mola sunfish can occur in coastal regions as well as offshore waters. But the preferred Mola mola habitat is an area where the water temperature is stable and generally a minimum of 10° Celsius (50° Fahrenheit).

Ocean Sunfish Characteristics

The genus Mola is noted as one that has fewer vertebrae than other bony fishes. As a consequence of that, their body shape is significantly shorter in length when compared to their height.

Apart from having a "laterally flattened" body, the overall appearance is one that's almost oval. The Mola mola fish is one that looks like a huge "swimming head" and a stunted tail - hence their slow, ungainly movements in water.

Here's the thing:

The body colouration of gigantic ocean sunfishes varies between white, silvery-gray, and brown - with some plain "countershading" for camouflage.

So, it is common to see a darker top section (dorsal) fading to a lighter shade at the bottom (ventral). The mucus covered skin is robust and leathery, almost like sandpaper.

Sometimes their thick skin becomes a host for parasites that will be removed by cleaner fish or seabirds. But, they do not have typical fish scales.

Sunfish mola are not usually aggressive and they are somewhat docile in nature. Even so, they will bite with their fused beak-like teeth if they're intimidated or harrassed. So, you should not touch a Mola mola!

Interesting Fact: Ocean sunfish (Mola mola) are part of the family Molidae. Despite being more compact, and a lot bigger in size, mola molas are closely related to boxfishes, pufferfishes, and triggerfishes.

Mola Mola Size and Weight

Adult molas regularly grow over two metres long. In fact, some fully grown sunfish can reach three (3) metres in total body length (10 feet) and measure four (4) metres tall (14 feet).

The biggest specimens can weigh more than 2,000 kilograms (4,400 pounds), making the Mola mola fish one of the heaviest of all bony fishes.

Mola Mola Behavioural Traits

Mola mola fish tend to be loners. Adults discontinue schooling as they mature.

The female sunfish is extremely fecund for a vertebrate, often laying more than three hundred million eggs.

Ocean sunfish are tagged in some areas of the world as they swim and feed.

But, they're not directly targeted as food and they don't have many natural predators.

Even so, there is some vulnerability for the species because they often get caught in fishing nets. Basic data from recent tagging tests suggest that this is a bigger problem than once thought and the ocean sunfish mola species may be in serious decline.

Different Types of Mola Fish

So, if you're into scuba diving you may be wondering how many species of Mola mola there are left in existence?

In fact, despite their strong physical characteristics, there are only three (3) remaining species of the genus Mola in the family Molidae.

Ocean sunfish (Mola mola)
Giant ocean sunfish (Mola alexandrini)
Hoodwinker sunfish (Mola tecta)

Although the family also includes the slender sunfish (Ranzania laevis) and sharptail mola (Masturus lanceolatus), the ocean sunfish is the most researched.

What Do Mola Mola Fish Eat?

Ocean sunfish are opportunistic, and somewhat generalistic, feeders that enjoy quite a varied diet. So for example, not only do these typical suction-feeders consume lots of gelatinous zooplankton, such as jellyfish and salps, they also eat:

Crustaceans (e.g., amphipods, krill, crabs, shrimp)
Fish larvae
Marine eelgrass (Zostera)
Siphonophores (e.g., Portuguese man o' war)
Small juvenile schooling fish
Soft-bodied marine cephalopods (e.g., squid)

Interesting Fact: Similar to blowfish poison effects on humans, Mola mola (ocean sunfish) also contains harmful toxins. However, despite being banned for consumption in most of Europe, some Asian countries still consider it as a delicacy, especially Japan, Korea, and Taiwan.

How Do Ocean Sunfish Reproduce?

Having an open-ocean lifestyle, closely resembling some pelagic shark species, is the main reason why Mola mola reproduction strategies still remain quite sketchy and understudied.

We do know that ocean sunfish reproduce through a process of external fertilisation. Thus, male sperm and female eggs are released into warm offshore water - simultaneously.

But wait - there's more:

In females, egg production is considered as being the highest number recorded of all marine vertebrates, typically laying up to 300 million per spawning event.

Yet, the eggs are miniscule in size, less than one (1) millimetre in diameter. Nonetheless, they are buoyant enough to float with planktonic material until they hatch.

Newly hatched ocean sunfish eggs are covered with spines, closely resembling the appearance of their boxfish and pufferfish counterparts.

Mola Fish Predators and Threats

Despite being one of the biggest vertebrates in the ocean, the Mola mola fish faces a number of natural predators and some significant threats due to human-related activities.

In the wild, ocean sunfish get attacked by several marine mammals, especially killer whales (orcas) and sea lions.

They also fall prey to some of the biggest shark species, such as great whites (Carcharodon carcharias) and tiger sharks (Galeocerdo cuvier).

Moreover, some of the worst human-related threats to the long term survival of the oceanic sunfish (Mola mola) include:

Bycatch or unintentional capture (getting entangled in drift gillnets and longlines)
Boat collisions (basking near the surface of the water makes them vulnerable to strikes from boat propellers)
Marine debris ingestion (many marine species mistake floating plastic bags for jellyfish which can lead to malnutrition and death, including sea turtles)
Climate change (warming seas disturbs prey distribution which in turn shifts ocean sunfish range to colder water, ultimately affecting their spawning success rates)

Pro Tip: The IUCN Red List of Endangered Species assessed the Mola mola fish phylum in 2011. They list sharptail mola and slender sunfish as "Least Concern" (LC). Still, they list ocean sunfish (Mola mola) as "Vulnerable" (VU) with a "Decreasing" population trend.

Related Information and Help Guides

Note: The short video [2:13 minutes] presented by "Deep Marine Scenes" contains some fascinating footage and even more Mola mola facts and information.