An Ocean sunfish

The Ocean sunfish is recognized as one of the largest/heaviest bony fishes across the globe. Studies show that at full maturity, this species of fish can weigh up to 1000 kg. The ocean fish derives its name from its pension for basking in the sun.

To do this, it will typically float on its side along the surface of the water. Another interesting feature about the ocean sunfish is its peculiar shape.

The best way to describe them would be to say that they resemble a large floating blob. Read more interesting facts about the Ocean sunfish right here.

Size and Weight.

Being the largest of all bony fishes, it comes as no surprise that an adult ocean sunfish can measure 1.8 meters in length. Additionally, they also measure in at 2.5 meters regarding their fin to fin length.

ocean sunfish in the wild
An ocean sunfish in the wild. (Image source:

These fish can also weigh anywhere between 247 to 1000 kilograms in the process. Interestingly, some individuals have recorded even more staggering measurements.

At the end of the spectrum, they can boast a length of 3.3 meters, weighing 2,300 kilograms. These behemoths additionally stretch about 4.2 meters from one fin to the other.

World Record Ocean sunfish.

Initially, the largest ever recorded ocean sunfish was thought to be a specimen trapped back in 1996 in Kamogawa, Chiba, Japan. This particular individual was about 2.72 meters (8ft 11 inches) long, with about 5,070 pounds to carry around.

However, this record was brought into question by a study conducted by three colleges: Hiroshima, Murdoch, and the University of Tokyo.

The three institutions all refuted the record under the claim that the documented individual was not an ocean sunfish. Back in 2006, a large ocean sunfish veered towards the Whangarei Heads in New Zealand. This individual was about 3.3 meters long.


With respect to their diet, the ocean sunfish is classified as a foraging predator. This means that they consume various prey, ranging from zooplankton, algae, small fishes, crustaceans to squid. However, their preferred meal of choice is the jellyfish.

Owing to their significant mass, the ocean sunfish has to eat a plethora of jellyfish to account for its mass. Another reason why they consume a lot of jellyfish is that they are relatively low in calories and nutrients; a good part of their genetic makeup is water.

This forces the ocean sunfish to hunt constantly. From its choice of diet, one can gather that this particular fish eats depending on where it is at the moment.

One common misconception about these fish is that they are a danger to people. It is a belief that stems from the ocean sunfish’s natural sense of curiosity. They have been known to swim quite close to divers.

A sunfish and a diver
(Image source:


Experts agree that, on average, an ocean sunfish can live up to 10 years in captivity. Their lifespan in the wild is something that remains undetermined, however.

This fish’s growth rate is also another thing that scientists are yet to determine, as well. Some unverified studies have suggested that the ocean sunfish can live up to 23 years in the wild.

Location and Habitat.

Ocean sunfish usually favor tropical and temperate oceans scattered across the world. These fish typically roam across the northern seas, the Mediterranean, the Pacific, Atlantic, and the Indian Ocean. Experts agree that these fish will stay 60 to 120 miles within the coastline.

Studies have also shown that these fish only migrate within their ranges (usually a 300-mile radius around the coastlines). Interestingly, one particular ocean sunfish was observed migrating across a 400-mile range.

These species are also rarely kept in captivity. In America, for instance, they can only be observed at the Monterey Bay Aquarium. Other aquariums they can also be found in include the Kaiyukan Aquarium located in Japan and the Lisbon Oceanarium set up in Portugal.

A sunfish in an aquarium.
Oceanarium in Hirtshals. (Image source:


In Japan, these fish have been recorded reproducing multiple times in October, towards the end of the summer. Studies have also shown that the ocean sunfish will attain sexual maturity between 5 and 7.

Owing to their size, a female sunfish can produce a ridiculous number of eggs. One such fish was found with about 300 million eggs in her body. Despite laying so many eggs, only a few of them will hatch. This is because only a few of them will survive as they are all scattered into the water.

The way the ocean sunfish reproduces can be described as ‘broadcast spawning.’ This occurs when the females lay their eggs as the males release their sperm into the water simultaneously.

Can the ocean sunfish be eaten?

Remarkably, the ocean sunfish is regarded as a delicacy in certain parts of the world. For instance, there is a large market for them in places such as Japan and Taiwan. They reportedly have a unique flavor that will appeal to most fish enthusiasts.

However, their consumption ,can pose a significant risk to one’s health, particularly if it is not prepared efficiently. Moreover, the ocean sunfish is listed as a vulnerable species by the International Union for Conservation of Nature. This makes it illegal to catch and subsequently eat them in most parts of the world.

Why is the Ocean sunfish listed as vulnerable?

By-catch, which occurs when a certain fish gets trapped in a net that was meant for different fish species, is one reason why the ocean sunfish’s population has dwindled.

Studies have shown that long line traps in places like South Africa accidentally trap about 340,000 ocean sunfishes every year.

Another worrying statistic was recorded in California, where about 14 to 60% of fish caught by swordfish fishermen are ocean sunfishes. At times, sunfish also confuse plastic, confusing waste material for jellyfish; this usually leads to suffocation.

Facts about the Ocean sunfish.

  • This particular species of fish is often plagued with a plethora of skin parasites. Scientists say that one sunfish can have as many as 50 different parasites on their skin. Consequently, most sunfish have to swim to the surface and attract sea birds such as albatross and gulls, which, in turn, eat the parasites from the sunfish’s body.
An ocean fish on its side.
An ocean fish on its side to alleviate the irritation caused by parasites. (Image source:
  • The Ocean sunfish’s scientific name is ‘Mola mola.’
  • This species of fish lacks a normally structured tail. Instead, the sun ocean fish comes equipped with a lumpy appendage known as a clavus. This evolved over time due to the fusion of anal fin rays and the fish’s dorsal.
  • The ocean sunfish can come in a variety of colors, ranging from white to gray.
  • Female sunfish are considerably larger than their male counterparts.
  • Ocean sunfish additionally have teeth that come together to form a beak-like structure.
  • The most glaring feature about the ocean sunfish is its shape, which can be described as bullet-like. This feature stems from the fact that their back fin never develops entirely.
  • These fish can be characterized as solitary creatures. Interestingly, they have been observed congregating to clean each other.

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