The Ocean Sunfish (Mola Mola) – A Weird and Wonderful Creature

Mola Mola Swimming Under The Sea
Mola Mola Swimming Under The Sea

You may have already heard that the Ocean Sunfish (Mola Mola) is one of the strangest creatures of the fish world living today. But why?

Given how cool they are, it’s surprisingly hard to find easy to understand information about them all in one place…

That’s why in this guide I’m going to take you down the winding history of the Ocean Sunfish and show you all the weird and wonderful things that make this gentle giant so legendary!

You’re about to learn some pretty strange things about our friend the Mola Mola…

So if you’re ready – Let’s start the adventure…

What’s the big deal?

Mediterranean swordfish fishermen hate it. The Japanese revere it. It’s a culinary delicacy in certain parts of Asia, and it’s been eaten by ancient cultures dating back 5000 years ago.

…yet, apparently, it tastes horrible.

It has the skin of a shark, beak-like structure teeth, and it’s missing a tail. And with a cruising speed of about 2 miles per hour, it’s in no hurry to get anywhere. 

Mysterious and Fascinating

It’s a swimming conundrum, a biological contradiction, and a sun-basking mystery. It’s the sunfish, the common mola, and it’s one of the ocean’s most amazing creatures!

Let’s go diving with the ocean sunfish. There’s plenty to learn…

By U.S. National Oceanic and Atmospheric Administration - U.S. National Oceanic and Atmospheric Administration, Public Domain,
Mola Mola in Deep Waters (2)

What’s in a Name and Who’s in the Family?

Sunfish is a beautiful name, a clear contrast to its appearance

It gets this name from its regular trips to the ocean surface where it appears to sunbathe, lazily soaking up the sun. This is where most people will get to spot the sunfish without diving. 

Most of us know the mola mola as the ocean sunfish – but this name can be pretty confusing at times because there are so many fish, saltwater and freshwater, that share it…

In Europe, it is called the “moon fish”, for Germans it’s the “swimming head”, and in Chinese it’s the wonderful “toppled wheel fish”.

So far, to avoid any confusion we won’t be using its scientific name which is genus Mola, we’re gonna use the term mola mola, it’s much cooler, right? But where does it come from?

It’s Latin of course and means millstone, a direct reference to the mola mola’s shape. From now on we’ll refer to it as the common mola.

There are Six Members of the Mola Sunfish, Family

  • The mola mola, or The common mola. Its cousins include;
  • The mola ramsayi, or short ocean sunfish
  • The mola tecta, or hoodwinker sunfish
  • The mola alexandrini, or bump-head mola
  • The masturus lanceolatus, or sharp-tailed mola
  • and ranzania laevis, the slender mola

While having a great many similarities, there are significant differences between the six sunfish. It would be very misleading to attribute common mola characteristics to its cousins.

It’s interesting to note that its close relatives include pufferfish and triggerfish:

Yep, it seems the entire extended family got hit with the weirdo stick. It’s an aquatic Adams family

While not as big as the ocean’s other gentle giants, they can still grow to be pretty massive. At 10.8 feet long and 14 feet across, you’re not going to fit the biggest of the species in your home aquarium…

Growing up to an average size of 6 feet by 8 feet and weighing up to 5 000 pounds, even the backyard pool is too small should you want one of the world’s heaviest bony fish as a pet!

Even the staff at the Monterey Bay Aquarium had to innovate different methods to properly handle and care for this kind of fish.


One of the first sunfish in captivity was kept in the Monterey Bay Aquarium.

They have a small mouth with fused teeth, resembling a beak. It also has teeth in its throat used for crushing and shredding as the food passes through to the stomach.

Staying Afloat with the Common Mola

In a strange evolutionary twist, the mola (largest bony fish) lacks a swim bladder, an important feature found in bony fish that is used to control buoyancy.

In a strange evolutionary twist, the mola lacks a swim bladder…

In that regard, it’s a little more like a shark that relies in part on fatty tissue in the liver that has positive buoyancy. 

Beneath its skin is a layer of jelly that ensures they remain neutrally buoyant. They suspend in the water, neither floating or sinking.

A Head with Fins?

Perhaps the best description of the fish was coined by the Germans who named them “Swimming Heads”. This is indeed what they look like… 

By Nol Aders - Own work, CC BY 2.5,
An Ocean Sunfish in Nordsøen Oceanarium, Hirtshals, Denmark (3)

There is no tail to speak of or the tail is not a generic caudal fin. It’s like the dorsal and anal fins have wrapped around it’s butt and joined together!

The pectoral fins, like their mouths, are so disproportionately small they look ridiculous – Their protruding dorsal fin would look far more at home on large sharks. In fact…

When they breach the open ocean surface they are often mistaken for shark fins.

Mola Mola’s use their dorsal and anal fins to swim…

Mola Mola’s use their dorsal fin and anal fin to swim by moving them back and forth in the same direction at the same time. Synchronously flapping, a little like a bird

It’s ungainly looking in such a strangely shaped fish, but certainly effective!

Its mouth is very small relative to its body, and the gills look like something far removed from your average bass, tuna or shark.

Sandpaper Skin with Teeth

Their skin color is primarily brown to silvery-grey or white with the dorsal side being darker. However…

Its skin color is often regional and known to change when feeling threatened. The skin is extremely rough and covered in denticles, much the same as sharks. 

Back in 1998, a ship docking in Sydney, Australia managed to get a 3000-pound common mola stuck to its bulbous bow…

This fish was struck only 100 miles from port, yet that was enough time for the skin of the fish to scrape off the ships paint down to bare metal

Living with Parasites

The common mola is highly prone to parasite infestations on its skin…

The common mola is highly prone to parasite infestations on its skin. There can be 40 different types of parasites on their skin at any one time.

Talk about making your skin crawl!

The fish will use other fish, and even ocean birds, in a critical symbiotic relationship, to help it remove the parasites from its skin.

The infestations are likely caused by their jellyfish diet (parasite hosts), combined with their slow swimming speeds.

See how that symbiotic relationship works in this awesome video from Nat Geo below…

Seagulls Helping Sunfish Remove Parasites

Another Way of Removing Parasites

It’s also been speculated that the reason for the sunfish’s frequent breaching (even reaching up to 10 feet), in an apparent effort to dislodge these parasites from its skin.

As we have stated, the common molar is often spotted during its sun-basking and surface breaches. The frequency of sightings probably has a lot to do with its very broad global distribution.

Global Distribution of the Common Mola

The common mola inhabits all the ocean’s tropical and temperate waters

While mainly inhabiting temperate and tropical oceans, it has been known to travel inshore, into the kelp beds and coral reefs in order to be cleaned of parasites. Interestingly, much of what science knows about common mola distribution is thanks to the general public reporting their encounters and sightings

By OBIS mapping software (July 2018 version) -, CC0,
Ocean Sunfish Distribution Map (4)

Despite its ungainly design, the sunfish does quite a bit of swimming up and down the water column…

The common range covers the ocean surface to a depth of 650 feet. However, tagged fish have been recorded as deep as 3,280 feet – well over half a mile.

Mola Mola at the Surface of Water
Mola Mola at the Surface of Water

Why Do Sunfish Bask in the Sun

the sunfish would bask in the sun to regulate their temperature…

Science generally agreed that the sunfish would bask in the sun by swimming near the surface to regulate their temperature.

Following dives to the darker, colder water depths, it would return to the surface and use the sun to warm up again. In many scientific circles this theory is still broadly accepted. 

That’s sunbaking with serious purpose, not for a holiday tan!

A recent study has thrown a little doubt on this theory…

Researchers discovered “Fish spent greater than 30% of their time in the top 10m of the water column, and over 80% of time in the top 200m…” .

Their observations and calculations did not prove any correlation between the common mola’s sun-basking and thermoregulation

Travelling With the Common Mola

Migratory habits have been difficult to ascertain, but tagging has proven that the common mola will travel as far as 1,100 miles

That’s a significant distance for a fish once thought as lazy and sluggish!

… this particular sunfish took 3 months to make the 1,100 mile journey.

Research suggests they get about the ocean by drifting with the current – Molas have been recorded swimming 16 miles in a day, cruising at about the speed of 2 miles per hour.

So, they’re not really in any hurry!

Migration is likely triggered by seasonal jellyfish movements, their preferred food source.

You can learn and contribute information about sightings of the ocean sunfish in this website by Marine Biologist and National Geographic explorer Tierny Thys – Learn more about her mission in the short clip below…

Strange Sunfish and Hope for the Ocean

Approximations suggest it takes 20 to 25 years for a Mola to reach full size

The heaviest specimens can reach up to 14 feet vertically and 10 feet horizontally, Yet there is little useful data to draw conclusions on actual life spans.

The Mola Takes a Chance on Love and Family

Current research has failed to shed any light on mating habits and rituals. Marine biology and scientific observations suggest that their breeding cycle is actually quite random and chancy…

Essentially, nearby males and females eject copious amounts of sperm and eggs into the water and just hope

there is no other known vertebrate that produces such astonishing numbers of eggs as the female common mola…

Interestingly, there is no other known vertebrate that produces such astonishing numbers of eggs as the female ocean sunfish…

A female may produce as many as 300 million eggs at a time, making them the most fecund fish. And you thought your hen had a good layer!

Her eggs are fertilized externally, following release into the water – they hatch releasing fish larvae that weigh mere fractions of an ounce and are 1/10th of an inch long. 

Following the transition to fry, their appearance barely resembles that of their parents. They look more like pufferfish, or a 5-year-old’s creative interpretation of a fish…or alien!

Juvenile molas swim together in schools; nature’s safety in numbers. As they mature, the schooling behavior ceases. A mature common mola is generally solitary, but they are known to be found in pairs. 

Public Domain,
Mola Mola Caught in 1910 Estimated Weight 3500 Pounds (5)

The Mola’s Extraordinary Growth

The most phenomenal attribute is its growth rate…

It’s the heaviest bony fish in the world!

A common sunfish can grow to more than 60 million times its birth size. Growth rates of young fish in captivity have been recorded at an average of 55 pounds per month. Very little is known, however, about growth rates in the wild.


An Ocean Sunfish in the Monterey Bay Aquarium grew up to 373kg in just 15 months.

The Common Mola Diet

Sharing the culinary desires of many sea turtles, the mola has a penchant for jellyfish

Researchers once believed their diet was restricted to jellyfish alone; however, recent studies suggest their diet is more diverse. What do they eat?

Regular menu items include siphonophores, comb jellies, slaps, small crustaceans, squids, small fish, and zooplankton. Yummy!

It was also believed that ocean sunfish mola mola were reasonably lazy with feeding, however, fish biology and science now agrees that sunfish are very active hunters, spending significant amounts of time feeding at depth.

Who and What Eats the Common Mola

The common mola has some pretty strong protection mechanisms, particularly when mature…

Firstly, its immense size is a significant deterrent for many predatory fish.

Secondly, it’s believed to taste pretty bad!

Thirdly, its skin can be up to 3 inches thick in places. 

Nonetheless, there are still several aquatic predators that see them as dinner. Sharks, orcas, and sea lions are known to include sunfish on their extensive menus.

Sea Lions have been witnessed attacking sunfish just for fun!

California sea lions, especially near the Monterey Peninsula, are known to bite a small ocean sunfish, then play with them like frisbees.

They will attack aggressively, toss them about with reckless abandon, eat their protruding fins, then leave the still living sunfish to die a miserable death.

Here is a video of a Sea Lion attacking an unfortunate sunfish..

Sea Lion Attacking an Ocean Sunfish

Juvenile common mola presents a much easier target… Fish such as bluefin tuna, mahi-mahi, and others, are known to target sunfish.

Of course, we humans also eat sunfish too…

In Taiwan and Japan, sunfish flesh is considered a delicacy. All parts of the fish are eaten, including the internal organs and fins. Parts of the sunfish are also considered important as traditional medicine.

Is The Common Mola Under Threat?

The International Union for Conservation of Nature (IUCN) regards the sunfish as being “vulnerable”

The sunfish is included on their red list – this means that their data concludes sunfish numbers are decreasing.

Further losses will see “vulnerable” escalate to endangered. Alarmingly, there are only two more steps past endangered to extinction. You can contribute to raising awareness about the sunfish by donating to the adopt a sunfish project by the National Geographic Explorer Tierney Thys.


It’s no wonder that it’s human activity that poses a significant threat to sunfish populations. With over 300,000 being caught as bycatch in South Africa alone.

Commercial Fishing practices are Indiscriminate

By and large, there’s no significant commercial market for the common mola. However…

Commercial fisheries that use long lines, drift gillnets, and midwater trawls often catch huge numbers of sunfish as bycatch. Often sunfish bycatch will significantly outweigh the catch of the target species.

The commercial catch of Mediterranean swordfish is often 90% sunfish. These professional fishermen are not particularly fond of the sunfish.

Harmful Practices

Sadly, commercial fishermen from certain cultures regard them as a pest. When accidentally caught, the fins are cut off and they’re thrown back into the water to die.

Discarded Plastic Kills

Ocean pollution is compounding the destruction of commercial bycatch…

Plastic litter has made its way into the food chain and sunfish are particularly susceptible.

By Edgard Dias Magalhães - Own work, CC BY-SA 3.0,
Mola Mola Sighting from Santiago Island, Galapagos (6)

Plastic bags look a lot like jellyfish…

Like other species and aquatic animals that feed on jellyfish and small fishes, sunfish are falling to mistaken identity, ingesting plastic bags thinking they’re a tasty jellyfish dinner

There are now countless scientific studies warning of the looming disaster plastic waste poses for not just sunfish, but the world’s entire oceanic ecosystem.

The Mola As Currency

In the 17th century Japan, the Shogun would accept sunfish instead of taxes owed…

Today, Japanese people enjoy swimming with sunfish. They are much loved and highly regarded in Japanese culture.

The Mola Mola App

Survive mola mola is a mobile phone game that is very popular in Japan… Over 6 million gamers all over the world play the game that involves nurturing a mola mola.

Don’t Kill a Mola!

The Polynesians believe the slender sunfish is the king of all mackerel, and that killing a slender sunfish will bring terrible bad luck!

Polynesians are coastal cultures, living by the sea, often on small islands. Fish and seafood are vital to their survival…

It is believed by many Polynesian cultures that if they kill a slender sunfish, the fish they traditionally eat will not find their way to traditional fishing grounds. With no fish available for catch, hunger and famine are likely.


Sunfish are frequently involved in collisions with boats of all types. Their enormous size can cause significant damage to the hulls of sailing boats. They also get caught in the propellers of ships, often causing damage to the vessels and themselves.

Wrapping Up the Common Mola. The Sunfish

Saying that the ocean sunfish is a weird-looking fish is an understatement

The animal kingdom has no shortage of weirdos, and the ocean sunfishes fit the bill for this distinguished list!

It’s nowhere near as ugly as the naked mole-rat or the coelacanth. And it doesn’t look at all as unloved as the Madagascan aye-aye does. It’s funny looking, yes! But perhaps not as cartoon-like as the dumbo octopus…

The common mola looks like it’s been assembled using a disparate bunch of spare parts, yet there’s a curious beauty and mystique about this fish…

A swimming head, the Germans call it. Yet it has a brain the size of a nut!

Unusual Features

The strange-looking ocean sunfish is at best (and worst) awkward looking…

And like many in the animal kingdom, its unique appearance seems to be a result of an unsolvable argument between mother nature and evolution

Regardless of the ocean sunfish ancient evolutionary path, it’s here with us, and it’s nothing short of amazing! Despite its ungainly appearance, there’s a grace to the ocean sunfish that defies its less than graceful look.

For many of us, it doesn’t matter how much we squint, the ocean sunfish always looks…well, a bit ugly

But beauty is in the eye of the beholder, as they say, and the ocean sunfish has a pretty big fan club who believes it’s very beautiful indeed.

  1. Mola Mola Swimming Under The Sea (Featured Image)
    By Per-Ola Norman – Own work, Public Domain,
  2. Mola Mola in Deep Waters
    By U.S. National Oceanic and Atmospheric Administration – U.S. National Oceanic and Atmospheric Administration, Public Domain,
  3. An Ocean Sunfish in Nordsøen Oceanarium, Hirtshals, Denmark
    By Per-Ola Norman – Own work, Public Domain,
  4. Ocean Sunfish Distribution Map By OBIS mapping software (July 2018 version) –, CC0,
  5. Mola Mola Caught in 1910 Estimated Weight 3500 Pounds
    By P.V. Reyes of Avalon, California. See: Peter Victor Reyes (1875-1950), photographer, on – Library of Congress, Prints and Photographs Division., Public Domain,
  6. Mola Mola Sighting from Santiago Island, Galapagos By Edgard Dias Magalhães – Own work, CC BY-SA 3.0,
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