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Oceanic Sunfish Fact File

Mola mola

Credit: Sonse, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons

Weight

2 tonnes

(2 tons)

Length

4m

(13ft)

Lifespan

Wild 20 years

Captive 20 years

Diet

Carnivore

Jellyfish

Conservation Status

IUCN

Vulnerable

The World's Largest Bony Fish!

The oceanic sunfish is the world's largest species of bony fish and can reach a width of up to 4m (13ft) across and 2 tonnes (2tons) in weight.

Despite their large size these animals mostly feed on jellyfish. These are collected using their jaw like mouth structure with the teeth fused in to a plate. Food is gradually broken in to small chunks.

Females produce the largest number of young of any animal. She may produce up to 300 million eggs in each clutch and produce multiple clutches each year.

This species is threatened through bycatch in fisheries and hunting for food and traditional medicines.

Read on to learn more about these fabulous fish.

Appearance

What does the Oceanic Sunfish look like?

The oceanic sunfish is the world's largest species of bony fish reaching a total length of up to 4m (13ft) across. They can weigh up to 2 tonnes.

Across the body their scales are colored grey.


Their body is a large circle and lacks a tail. Instead the body ends with a fleshy frill. On both the top and bottom of the body are a large, triangular fin. These are used to push them through the water. A pair of smaller fins sit on either side of the body near the eye.


Small eyes are present on either side of the face.

Adaptations

How does the Oceanic Sunfish survive in its habitat?


Their jaw teeth are fused to form a beak which can be used to find their food.

Inside of their digestive tract the ocean sunfish has a special mucuslike lining which helps to protect it against the stinging tentacles of the jellyfish.

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Diet

What does the Oceanic Sunfish eat?

The oceanic sunfish is a carnivore. Their primary food source is jellyfish. Fish, molluscs, plankton and crustaceans are also consumed. Their beak is used to nip off pieces of food.

Due to the low quality of nutrients in jellyfish they must feed on large numbers to sustain them.

Instead of chewing their food they will gradually move it in and out of their mouth which gradually breaks it in to manageable chunks.

Learn more about the Oceanic Sunfish in this video from Data Truck on YouTube

Range

Where do you find the Oceanic Sunfish?

Oceanic sunfish have a wide range which takes in tropical and sub-tropical waters across the globe. Their range extends as far North as the waters off of British Colombia.


They can be found at depths of up to 400m (1312ft) below the surface.

Habitat

Where can the Oceanic Sunfish survive?

These fish live in the ocean primarily being found in pelagic habitats. It is most common to find them at slopes where they can come in to the shallows to find shelter and cleaner fish.

Oceanic Sunfish (Mola mola)

Credit: Public Domain

Reproduction

How does the Oceanic Sunfish produce its young?

Each female may produce as many as 300 million eggs. These are fertilized through broadcast spawning. This is where the male releases sperm at the same time the female releases her eggs.

At hatching the young are just 1cm (0.4in) across and will increase their size 60 million times over during their life. The fry have small spines across their body which help to protect them.

Young known as fry may swim around schools for protection.

While no reliable records of the oceanic sunfishes age at maturity have been produced scientists estimate that it occurs between 5 and 7 years old.

Behavior

What does the Oceanic Sunfish do during its day?

This species is regularly sighted lying on its side at the oceans surface basking in the sunshine.

These animals are solitary. They come together at cleaning stations in small groups.

Previously thought to just cruise on the ocean currents the oceanic sunfish can actually propel itself through the water reaching speeds of up to 3.2km/h (2 miles).

To remove parasites from their skin they will visit cleaner fish stations where small fish eat the parasites for them. When they are floating on the surface some birds may also eat the parasites.

Oceanic Sunfish (Mola mola)

Credit: Yohann Cordelle, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Predators and Threats

What stops the Oceanic Sunfish from surviving and thriving?

This species is hunted by orcas, sea lions and large shark species. The California sea lion has been observed biting off a fin and then playing with it rather than eating it.

A range of parasites have been observed attached to the oceanic sunfish. This included barnacles which were found living inside of their throat.

Populations of the oceanic sunfish are believed to be in decline. Most of this data has been recorded through decreases in the presence of this species as bycatch in fisheries.


This species is a regular victim of bycatch. Often there may be more oceanic sunfish in a net than the species which fishers are targeting.


As their favorite food is jellyfish they may consume plastic bags which they confuse for this food source.

While this species is not popular for food some are captured for this purpose. They are also used in some traditional medicines.

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Quick facts

Their scientific name is taken from the Latin word for millstone in reference to the near circular shape of the body.

This species may also be known as the common sunfish, mola or short sunfish.

They were first described for modern science during 1758.

Oceanic Sunfish (Mola mola)

Credit: Nol Aders, modifications by PaladinWhite, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

References

Liu, J., Zapfe, G., Shao, K.-T., Leis, J.L., Matsuura, K., Hardy, G., Liu, M., Robertson, R. & Tyler, J. 2015. Mola mola (errata version published in 2016). The IUCN Red List of Threatened Species 2015: e.T190422A97667070. Accessed on 25 March 2022.

Ducksters.com. 2022. Animals: Ocean Sunfish or Mola Fish. [online] Available at: <https://www.ducksters.com/animals/ocean_sunfish_mola.php> [Accessed 26 March 2022].

Montereybayaquarium.org. 2022. [online] Available at: <https://www.montereybayaquarium.org/animals/animals-a-to-z/ocean-sunfish> [Accessed 26 March 2022].

Fishesofaustralia.net.au. 2022. Mola mola. [online] Available at: <https://fishesofaustralia.net.au/home/species/785/> [Accessed 26 March 2022].

Oceana. 2022. Ocean Sunfish. [online] Available at: <https://oceana.org/marine-life/ocean-sunfish/> [Accessed 26 March 2022].

The Australian Museum. 2022. Ocean Sunfish, Mola mola (Linnaeus, 1758). [online] Available at: <https://australian.museum/learn/animals/fishes/ocean-sunfish-mola-mola/> [Accessed 26 March 2022].

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