The Strange, Strange Ocean Sunfish

The ocean sunfish is the heaviest known bony fish, weighing an average of between 247 and 1,000 kg (545–2,205 lb).

They are rather monstrous to look at – all flattened and disheveled. Even their Latin name is a bit of a diss – Mola mola – meaning ‘mill stone’ because they’re grey and sort of circular.

It’s not an attractive fish, if we’re going to be honest about it.

Looks aside, the sunfish certainly does cut a daunting shadow. The largest Mola mola found to date was 3.2 m (10.5 ft) in height; in other words: huge.

At the bottom of this article is a video showing a few divers interacting with a sunfish; the featured fishie isn’t quite as large as that, but it gives you an idea of the impressive girth of these gentle monsters.

There are a lot of strange things about the sunfish (other than their shape). None of them are particularly startling on their own, but when taken together, they are marvellous:

• It has fewer vertebrae and a shorter spine in relation to body size than any other fish.

• Sunfish predominantly eat jellyfish, and because jellyfish have very little nutritional content, they have to spend the vast majority of their day feasting on them to maintain their massive bulk.

• Ocean sunfish produce more eggs than any other vertebrate – 300,000,000 in one go.

• The sunfish’s teeth are fused into the shape of a beak, apart from two pharyngeal teeth which can be found in its throat.

• Most bony fish use a swim bladder to maintain buoyancy and control their depth. The sunfish hasn’t bothered with one.

• Mola mola’s skin can be up to 7.3 cm (2.9 in) thick in places and is covered by a layer of mucus rather than scales.

• The poor sunfish is plagued by parasites, and more than 40 different species enjoy its company. He enlists the help of various fish and birds to clean them. They have even been known to half-beach themselves in desperate efforts to get rid of the unwanted guests.

• The ocean sunfish lives in warmer waters and, if it gets too cold, it flaps about on the surface getting “recharged” by the sun. Like so:

• Sea lions hunt sunfish for fun. They have been observed biting off the fins and tossing around the body before eventually leaving the helpless floundering body to die.

• Sunfish have (arguably) the most extreme size growth of all vertebrates. Starting off at a tiny 2.5mm in length they can expand to 60 million times their birth weight.

Check out this video of one in “action”:



Quite an odd looking creature. But impressive. Sunfish aren’t endangered, they are fairly numerous, and can be found in warmer water throughout the earth’s oceans.

Their biggest predator, of course, is humans. But we only catch them accidentally. Although they are eaten in Japan and Taiwan, in general, they are considered bycatch and discarded.

All in all, I reckon this gentle giant deserves our respect and admiration. It’s not easy being slow and ugly in a sea filled with handsome speed freaks.

MORE FROM THE OCEAN:

THE INCREDIBLE SAILFISH

THE SECOND LARGEST ANIMAL ON EARTH

THE WEIRD WINGHEAD SHARK