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Marine Species: The Elusive Mola Mola

Divers who have been lucky enough to see a mola mola underwater don’t soon forget the experience. And despite the animal’s size, mola mola — also known as moonfish and ocean sunfish — are not easy to spot.

What is a mola mola?

Not only are mola mola hard to spot, but also quite mysterious. Researchers have not dedicated a lot of time to this huge fish, the largest bony fish in the ocean. Mola mola start out very small and strange looking, as sunfish eggs that turn into larvae only 2 to 3 mm long. These small eggs grow into a fish that can be almost 10 feet (3 m) from fin to fin. We know very little about their spawning grounds or reproductive cycle. They do have incredible reproductive potential, with more than 300 million eggs in the ovary of each female. Their lifespan is an enigma, but scientist think they can live up to 80 years.

Where do they live?

The oceanic sunfish lives in all temperate and tropical oceans and seas. Molas are frequently spotted in the Mediterranean, the Galapagos, the West Coast of the United States, and Nusa Lembongan/Nusa Penida off the coast of Bali. This location is also home to PhD research student, Marianne Nyegaard, who has been carrying out research on the mola mola in general, and the population around Bali for the past few years.

Research shows that sunfish can dive to extreme depths, over 2,000 feet (600 m), despite the very cold temperature at these depths. However, they also frequent shallow waters, and will show themselves to divers when they come to the surface, or near a reef, to visit cleaner fish, which remove their parasites.

The sunfish has no tail and a very distinct body shape — truncated, flat and round. They feed mainly on jellyfish, which they shred in their mouth before digesting it.

Some of their behavior is subject to hypothesis since scientific knowledge is limited. You’ll often see molas floating at the surface on their side. Recent research indicates that this behavior helps them warm up in the sun after long, deep dives, or assists birds that are feeding on their parasites. You’ll also sometimes see them breaching the surface, after a vigorous swim up from the deep. This could be another way of shaking parasites off their body.

Who is a threat?

Sharks and orcas prey on mola mola. Some countries, such as Japan and Taiwan, fish molas for their meat. Boats frequently hit them as well, and their size and weight can cause quite a bit of damage to ships.

Around divers they are usually pretty shy, and despite their odd appearance, they can swim away very fast. If you are lucky enough to see one, don’t scare it off — relax and enjoy this amazing and rare encounter.