OCEAN SUNFISH: MOLA MOLA

Mola mola (Linnaeus, 1758)

The massive docile ocean sunfish or common mola, Mola mola (Linnaeus, 1758) is one of the two heaviest known bony fish in the world — the other being the southern sunfish of the same genus. 

As a family, Molidae emerged between 45 million and 35 million years ago, well after the dinosaurs disappeared and at a time when whales still had legs. 

A group of pufferfishes — the kissing cousins to the Mola we know today and built like little tanks — left the safety of the coral reefs for the open ocean. 

They evolved and gave rise to Mola about 23 – 20.4 million years ago. These were followed by their still extant cousins, the Ranzania, 16 – 13.8 million years ago. The third genus of extant sunfish, Masturus, has not been identified in the fossil record (Carnevale et al. 2020) though we will keep looking and put that puzzle piece in its place in time.

When they are born, dozens would fit in the palm of your hand — each roughly the size of a pea. When they are youngsters, they are very curious and will swim up to you to take a wee nibble to figure out what you are. My mother had such a harmless bite when she was travelling as a girl. The bite left a tooth embedded in her leg that worked its way out a few weeks later. Not in any way perturbed, she speaks of her encounter fondly. 

As they grow, Mola take on a very roundish look and grow to a massive 247 to 1,000 kg (544 to 2,204 lbs) — that's one and a half times the size of a typical cow and bigger than a Grizzly Bear. The heaviest specimen on record is a bump-head sunfish, Mola alexandrini, caught off Kamogawa, Chiba, Japan, in 1996. It weighed 2,300 kilograms (5,070 pounds) and measured 2.72 metres (8 feet 11 inches) long.

The sheer size and thick skin of an adult of the species deter many smaller predators, but younger fish are vulnerable to predation by bluefin tuna and mahi-mahi. 

Adults are often consumed as tasty snacks by orca, sharks and sea lions — and sadly, by humans, particularly those from Japan, Korea and Taiwan. Fortunately, the EU has banned the sale of common mola and others within the family Molidae. 

Of all the fish we have in our oceans, the common mola or sunfish has the most names I have ever come across. 

Many of the sunfish's various names allude to its round, flattened, moonish or millstone shape. Its scientific name, mola, is Latin for millstone. It is a rather good choice as the fish resembles a millstone you might use for grinding grain, in part because of its grey colour, rough texture, and rounded body. 

Its English name, sunfish, refers to the animal's habit of enjoying the sun's rays as it basks near the surface. Its common names in Dutch, Portuguese, French, Spanish, Catalan, Italian, Russian, Greek, Norwegian, and German — maanvis, peixe lua, Poisson lune, pez luna, peix lluna, Pesce luna, рыба-луна, φεγγαρόψαρο, månefisk and Mondfisch, respectively — mean moonfish, in reference to its round moonish shape. 

In German or auf Deutsch, the common mola is also known as Schwimmender Kopf or swimming head. In Polish, it is named samogłów, meaning head alone or only head, because it lacks a true tail. In Swedish, Danish and Norwegian it is known rather unflatteringly as klumpfisk, in Dutch klompvis, in Finnish möhkäkala — all of which mean lump fish. 

The Chinese translation of its name is fān chē yú 翻車魚, meaning toppled wheel fish — perhaps as a wee homage to the original Latin mola or millstone. 

By any name, we find these gentle giants cruising through tropical and temperate waters around the world where they have thrived for many millions of years.