Ocean sunfish

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With a tall, flat body that looks like a fish cut off behind, the ocean sunfish is one of the heaviest bony fish, reaching about a tonne. It eats mostly jellyfish and is often seen lying on its side at the surface, basking in the sun.

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At a glance

Class: Fish
Diet: Meat eater (carnivore)
Weight: about 1,000 kg
Length: about 1.8 m
Conservation status: Vulnerable (IUCN VU)
Habitat: open ocean

Quick answers

Where does the Ocean sunfish live?

It lives in the open ocean of the Pacific, Atlantic and Indian oceans.

How big is the Ocean sunfish?

It grows to about 1.8 m and 1,000 kg.

What does the Ocean sunfish eat?

Its diet: meat eater (carnivore).

Is the Ocean sunfish endangered?

It is listed as Vulnerable (IUCN VU).

The ocean sunfish, or mola, is one of the biggest bony fish in the world and one of the strangest-looking. It looks like a huge fish head with no tail, with a tall flat body that can be as tall as it is long, around 1.8 metres. Most adults weigh between about 250 and 1,000 kilograms. It lives in warm and temperate seas all around the world.

It is often seen lying on its side near the surface, which looks like sunbathing and gives it its name. In many languages it is called moon fish because of its round shape. It eats mostly jellyfish and similar soft animals, so it has to eat a lot. One female can lay up to about 300 million eggs, more than any other known vertebrate. It is listed as vulnerable.

A fish like a swimming head

The sunfish has no real tail. Instead a rudder-like fin at the back helps it steer, and its tall dorsal and anal fins sweep side to side to move it along. Its mouth is small and beak-like. Young sunfish look like tiny puffer fish, quite different from adults. In Japan, Korea and Taiwan the sunfish is eaten, but in the European Union it is banned from sale.

Heaviest bony fish?

Sunfish have long been said to be the heaviest bony fish, with records of more than two tonnes. Scientists now know that this record belongs to a close relative, Mola alexandrini, which was once mistaken for the common ocean sunfish. Mola mola is still huge and still one of the largest ray-finned fish. Sunfish are often caught accidentally in nets, and floating plastic can also harm them.

Fun facts

It is one of the heaviest bony fish and often lies on its side at the surface to bask in the sun.
A female may lay up to about 300 million eggs.
Its name sunfish comes from sunbathing at the surface.
In many languages its name means moon fish.
It has no real tail, so it looks like a swimming head.