# Ocean Sunfish (*Mola mola*)

> The ocean sunfish, or mola, is the heaviest bony fish in the world, reaching up to about 2,000 kg and 3 m across in the largest specimens. Found in temperate and tropical oceans worldwide, it is a harmless drifter that swims slowly at up to 5 km/h and feeds mostly on jellyfish. Molas are famous for basking flat at the surface, live around 8 to 10 years, and are classed as Vulnerable.

- **Category:** Fish
- **Conservation status (IUCN):** Vulnerable
- **Range:** All temperate and tropical oceans — pelagic species occasionally seen basking at surface worldwide.
- **Canonical page:** https://globalanimalguide.org/animals/ocean-sunfish/
- **Last reviewed:** 2026-07-16

## Scientific classification

- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Actinopterygii
- **Order:** Tetraodontiformes
- **Family:** Molidae
- **Genus:** Mola

## Facts at a glance

| Attribute | Value |
| --- | --- |
| Scientific name | Mola mola |
| Diet | Carnivore — jellyfish, salps, and small fish |
| Habitat | Temperate and tropical oceans worldwide |
| Lifespan | 8–10 years in the wild |
| Weight | 250–2,000 kg (550–4,400 lb); record specimens heaviest bony fish |
| Top speed | Up to 5 km/h (3 mph); slow swimmer |
| Conservation status | Vulnerable (IUCN) |

## The heaviest bony fish

The ocean sunfish holds the record as the heaviest bony fish on Earth, with the largest individuals weighing up to about 2,000 kg (4,400 lb) and measuring around 3 m from fin tip to fin tip. Its body looks like a giant swimming head that ends abruptly, because it never develops a normal tail. In place of a tail it has a rounded rudder called a clavus, formed from the back of the body.

## A slow, gentle swimmer

Despite its bulk, the sunfish is a harmless, placid animal that poses no danger to people. It swims slowly, reaching only about 5 km/h (3 mph), by sculling its tall dorsal and anal fins from side to side rather than beating a tail. Molas often let currents carry them and glide gently through open water in search of food; they never run, because they are fish and move only by swimming.

## Feeding on jellyfish

The ocean sunfish feeds mainly on jellyfish and other gelatinous drifters such as salps and comb jellies, supplemented by small fish, squid, and crustaceans. Because this prey is mostly water and low in energy, a mola must eat huge quantities to sustain its size. It uses beak-like fused teeth to bite off chunks and a throat lined with spiny projections to break the slippery food apart.

## Basking and parasites

Sunfish are often seen lying flat on their sides at the ocean surface, seemingly sunbathing. This basking behaviour helps them re-warm after deep dives into cold water and lets seabirds and cleaner fish pick parasites from their skin. Molas carry an exceptional parasite load, and they will even leap clear of the water, perhaps to dislodge unwanted hitchhikers.

## Reproduction and record fertility

Female ocean sunfish are among the most fecund of all vertebrates, capable of carrying hundreds of millions of tiny eggs at once. The larvae hatch as spiny, spherical specks barely a few millimetres long, then grow through one of the largest size increases of any animal. Only a minute fraction survive the journey to adulthood.

## Conservation and threats

The ocean sunfish is listed as Vulnerable by the IUCN. Large numbers are caught accidentally as bycatch in gillnet and longline fisheries, where their slow, surface-bound habits make them easy to snag. Floating plastic bags, which resemble jellyfish, are also mistaken for prey, adding to the pressures on this ocean giant.

## Frequently asked questions

### How big is an ocean sunfish?

The ocean sunfish is the heaviest bony fish in the world, with the largest specimens weighing up to about 2,000 kg (4,400 lb) and reaching around 3 m across. Typical adults are smaller, in the range of a few hundred kilograms.

### Are ocean sunfish dangerous to humans?

No. Ocean sunfish are harmless, gentle animals with no interest in people and no ability to harm them. They swim slowly and feed on jellyfish, so divers can watch them at close range safely.

### What do ocean sunfish eat?

Ocean sunfish feed mainly on jellyfish and other gelatinous animals such as salps, along with some small fish, squid, and crustaceans. Because this prey is low in energy, they must eat large amounts to maintain their enormous size.

### Why do sunfish lie on their side at the surface?

Sunfish bask flat at the surface to re-warm their bodies after diving into cold, deep water. Basking also lets seabirds and cleaner fish remove the many parasites that collect on their skin.

### How fast can an ocean sunfish swim?

Ocean sunfish are slow swimmers, reaching only about 5 km/h (3 mph). They move by waving their tall dorsal and anal fins from side to side and often drift with the current.

### Are ocean sunfish endangered?

Ocean sunfish are listed as Vulnerable by the IUCN. Their main threat is accidental capture as bycatch in fishing nets and longlines, and they can also die from swallowing floating plastic mistaken for jellyfish.

## Sources

- [IUCN Red List — Mola mola.](https://www.iucnredlist.org/search?query=Mola%20mola&searchType=species)
- [Animal Diversity Web — Mola mola. University of Michigan Museum of Zoology.](https://animaldiversity.org/accounts/Mola_mola/)

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Source: Global Animal Guide (https://globalanimalguide.org/animals/ocean-sunfish/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.