American Oceans

Ocean Sunfish

The ocean sunfish, also known as Mola mola, is a fascinating species of bony fish that belongs to the family Molidae. It is the heaviest known bony fish in the world, with some individuals weighing over 2,000 kg.

a mola mola sunfish swimming in the water

Despite its size, the ocean sunfish feeds mainly on plankton and jellyfish, which it consumes in large quantities.

Despite its vulnerability, the ocean sunfish is still a common sight in temperate waters around the world. Its evolution and ecology continue to be studied by researchers, who hope to gain a better understanding of this enigmatic species.

In this article, we will explore the biology and behavior of the ocean sunfish, as well as its common names, teeth, and sightings.


Mola tecta

The ocean sunfish, also known as Mola mola, is a unique and fascinating creature that belongs to the family Molidae.

It is the largest bony fish in the world, with an average length of 1.8 meters and a weight of up to 2,300 kilograms.

Its body is flattened and disc-shaped, with a truncated tail fin. Its skin is thick and covered with mucus, which gives it a slimy appearance and helps protect it from parasites and predators.

The morphology of the ocean sunfish is characterized by its lack of a true tail fin, which is replaced by a clavus, a structure that resembles a rudder.

Its body is composed of a series of ossicles, which are small, bony structures that provide support and protection. The ossicles are arranged in a circular pattern around the body and are covered by a layer of skin and mucus.

The ocean sunfish is an omnivorous animal that feeds on a variety of prey, including jellyfish, squid, crustaceans, and small fish.

Its diet can vary depending on its size and age, with smaller individuals consuming more zooplankton and larger individuals consuming more fish.

The ocean sunfish has a high caloric requirement and can consume up to 60% of its body weight in a single day.

The growth rate of the ocean sunfish is slow, and it can take up to 10 years for an individual to reach sexual maturity.

Newly hatched ocean sunfish are tiny, measuring only a few millimeters in length. As they grow, they undergo a significant transformation in shape, with their body becoming more flattened and disc-like.


an ocean sunfish swimming in the water

Ocean sunfish, also known as Mola mola, are found in temperate and tropical oceans around the world. They prefer to live in the open ocean, where they can swim freely and feed on their preferred diet of jellyfish, salps, and other small organisms.

Ocean currents play a significant role in the habitat of ocean sunfish. Sunfish are known to follow the currents as they move around the ocean, which allows them to travel long distances and access new food sources.

In the Pacific Ocean, for example, ocean sunfish are often found in the California Current, which runs along the western coast of North America. In the Atlantic Ocean, they can be found in the Gulf Stream, which flows from the Gulf of Mexico to the North Atlantic.

In addition to following ocean currents, ocean sunfish are also known to migrate seasonally. For example, in the Southern Ocean, sunfish are found in higher numbers during the summer months, when food sources are more abundant.

During the winter, they move to deeper waters, where they can conserve energy and avoid predators.

Physical Characteristics

Mola Mola Sunfish

Ocean sunfish, also known as Mola mola, are one of the heaviest bony fish in the world. They have a unique appearance that makes them easily recognizable.

This section will discuss the size, shape, and fins of the ocean sunfish.


Adult ocean sunfish can grow up to 3.3 meters (11 feet) in length and weigh up to 2,300 kg (5,100 lb). They are the largest of the bony fish species.

However, they start their life as tiny larvae, measuring only a few millimeters in length.


The ocean sunfish is a flattened, disc-shaped fish with a round body and a short, stubby tail. They have a unique beak-like structure that protrudes from their head, which they use to catch prey.

The body of the ocean sunfish is covered in a thick layer of mucus, which protects them from parasites and other harmful organisms.


The ocean sunfish has several fins, including the dorsal and anal fins and the pectoral fins. The dorsal and anal fins are fused together to form a single fin that runs along the top and bottom of the fish.

This fin is used for stability and propulsion. The pectoral fins are located on the sides of the fish and are used for steering and maneuvering.

The ocean sunfish also has a unique feature called the rounded clavus, which is a thickened area at the base of the tail.

This feature helps the fish to swim more efficiently by reducing drag.

The fin rays of the ocean sunfish are not attached to the bones of the fins, which allows them to move independently.

This gives the fish greater control over its movements and helps it to navigate through the water more effectively.


Ocean sunfish, also known as Mola mola, have a unique diet that changes as they grow. They are primarily known for their diet of jellyfish, which makes up a significant portion of their diet.

They are also known to eat other gelatinous creatures such as salps, and ctenophores. A study conducted by Ackman in 1997 found that ocean sunfish and leatherback turtles share a diet that contains jellyfish and that the presence of certain fatty acids in both species is an indicator of a jellyfish diet.

As juveniles, ocean sunfish consume small crustaceans such as copepods and euphausiids. As they mature, they shift their diet to larger prey such as jellyfish.

However, they are opportunistic feeders and will eat a variety of prey including small fish, squid, mollusks, brittle stars, pufferfish, and porcupinefish.

While jellyfish make up a large portion of their diet, ocean sunfish have also been observed consuming algae.

In a study conducted by DNA barcoding, it was found that ocean sunfish have a cosmopolitan diet that includes a variety of prey from different ocean regions.


a diver swimming alongside a mola mola sunfish

Ocean sunfish, also known as Mola mola, have unique behaviors that set them apart from other fish species.

One of the most notable behaviors of ocean sunfish is their tendency to sunbathe, or bask in the sun near the surface of the water. This behavior is thought to help the fish regulate their body temperature and may also aid in the removal of parasites from their skin.

Ocean sunfish are also known for their impressive tracking abilities. They can navigate through the open ocean, covering large distances in search of food or mates. Some studies have shown that ocean sunfish are capable of traveling more than 5,000 miles in just a few months.

When not sunbathing or tracking, ocean sunfish spend much of their time foraging for food. They primarily consume jellyfish, but have also been known to eat small fish, squid, and even the occasional piece of plastic debris.

Despite their large size, ocean sunfish have a number of natural predators. Killer whales and sea lions are known to prey on these fish, and even large sharks have been known to attack them.

To defend themselves, ocean sunfish have a unique defense mechanism: they can release clouds of sperm and eggs into the water, which can confuse and deter predators.


a mola mola sunfish swimming underwater

Ocean sunfish have a unique reproductive biology that is not fully understood. Very few studies have been conducted on the reproductive biology of ocean sunfish, and the reproductive seasonality for M. mola in different locations is less well known.

Female ocean sunfish produce a large number of eggs, with some estimates suggesting that they can produce up to 300 million eggs at a time.

The eggs are small, measuring around 1.5 mm in diameter, and are released into the water column. The eggs are buoyant and are carried away by the currents.

It is believed that ocean sunfish do not reach sexual maturity until they are several years old, and their reproductive lifespan is not known.

Some studies suggest that ocean sunfish may reproduce throughout the year, while others suggest that they have a specific reproductive season.

Despite the lack of knowledge about the reproductive biology of ocean sunfish, there have been reports of large aggregations of ocean sunfish in certain areas during the spawning season.

These aggregations may be related to the reproductive behavior of the fish, but more research is needed to understand this phenomenon.

Conservation Status

a mola mola sunfish in the wild

The ocean sunfish (Mola mola) is listed as Vulnerable on the IUCN Red List of Threatened Species. This means that the species is facing a high risk of extinction in the wild.

The conservation status of the ocean sunfish was updated to Vulnerable in 2018 due to the species’ susceptibility to bycatch in fisheries and the increasing demand for their flesh in some parts of the world.

The ocean sunfish is a large, slow-moving fish that is often caught accidentally in fishing gear.

The species is also targeted by some fisheries for their meat, skin, and liver oil. The growing demand for ocean sunfish products in some countries has led to concerns about the sustainability of their populations.

Despite their large size, ocean sunfish are relatively fragile and vulnerable to injury and stress.

They are often injured or killed during fishing operations, and their populations are declining in many parts of the world.

To conserve the ocean sunfish, it is important to reduce the impact of fishing on their populations. Some measures that have been proposed include:

  • Reducing bycatch in fisheries through the use of more selective fishing gear
  • Implementing fishing quotas and regulations to limit the harvest of ocean sunfish
  • Educating consumers about the importance of sustainable fishing practices and the conservation of marine species

In addition to these measures, scientists are also studying the biology and ecology of the ocean sunfish to better understand their populations and inform conservation efforts.

Published research on the species is helping to identify key threats and conservation priorities, and to develop strategies for protecting the ocean sunfish and other vulnerable marine species.

Research and Studies

a mola mola swimming with small reef fish

Ocean sunfish have been the subject of numerous research studies over the years. One of the most notable studies was conducted by Tierney Thys, a marine biologist who has been studying sunfish for over two decades.

Thys and her team have conducted several studies on sunfish behavior, including their feeding habits and migratory patterns.

Another study, conducted by researchers at Kamogawa Sea World in Japan, focused on the sunfish’s unique physical characteristics.

The researchers found that the sunfish’s “schwimmender kopf,” or “swimming head,” allows the fish to move quickly and efficiently through the water.

Sightings of sunfish have also been documented by researchers all over the world. In Monterey Bay, California, researchers at the Monterey Bay Aquarium have been tracking sunfish sightings for years.

They have found that sunfish tend to congregate in certain areas during certain times of the year, which has helped researchers better understand their migratory patterns.

Frequently Asked Questions

What do ocean sunfish eat?

Ocean sunfish primarily feed on jellyfish and other gelatinous organisms. They have also been known to eat small fish, crustaceans, and squid. Due to their large size, they can consume a significant amount of food each day.

Where are ocean sunfish commonly found?

Ocean sunfish are found in tropical and temperate waters around the world. They are commonly found in the Atlantic, Pacific, and Indian Oceans. They prefer warm waters and are often found near the surface.

How large can ocean sunfish grow?

Ocean sunfish can grow to be very large. They are the heaviest bony fish in the world, with some individuals weighing over 2,000 pounds. They can also grow to be very long, with some individuals reaching lengths of 10 feet or more.

What are the predators of ocean sunfish?

Despite their large size, ocean sunfish have a number of predators. Sharks, killer whales, and sea lions have been known to prey on ocean sunfish. They are also vulnerable to human activities such as fishing and pollution.

Do ocean sunfish migrate?

Ocean sunfish are known to make seasonal migrations, but the details of these migrations are not well understood. They are believed to move to deeper waters during the winter months and return to shallower waters during the summer.

What is the lifespan of an ocean sunfish?

The lifespan of an ocean sunfish is not well known, but it is believed to be around 10 years. However, some individuals may live longer. The exact lifespan of an ocean sunfish may vary depending on factors such as diet, environment, and predation.

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