Gentle Giants

Sunfish are the largest bony fish in the ocean. They can grow up to 3m in length and approximately 2000kg in weight. Ocean sunfish are found in all the oceans of the world, excluding the icy polar seas.

There are two species of sunfish found in the waters surrounding Cape Town: the ocean sunfish (Mola mola) and the sharptail sunfish (Masturus lanceolatus). Sharptail sunfishes are found only in warmer waters, thus they are extremely rare in the local waters.

In recent years, a number of slender sunfish (Ranzania laevis) have also washed up on Cape Town beaches. These sunfish are believed to be the rarest of all sunfish species. Only ocean sunfishes (Mola mola) have been displayed in the Two Oceans Aquarium.

The Two Oceans Aquarium assists international researchers of sunfish with the collection of DNA samples when Aquarium staff come across a sunfish in Cape Town waters.

An ocean sunfish, spotted in Granger Bay. Photo courtesy Marius Acker

Interesting facts about these gentle giants:

  • Sunfishes are so called because of their habit of drifting at the surface as if basking in the sun
  • Sunfishes do not have tails as other fishes do – the caudal (tail) fin has been replaced by a rudder-like structure. The ocean sunfish has a rounded, wavy rudder. The sharptail’s rudder, as the name suggests, has a distinct point
  • All sunfishes have small mouths and the teeth are fused together in each jaw, forming a beak like that of a parrot. The beak is internal and hidden from view
  • Sunfishes feed on jellies. It is remarkable that an animal that grows to such a large size subsists on a diet with very little nutritional value
  • Sunfishes are not considered edible as they consist mainly of cartilage and gristle and their flesh is soft and insipid. Also, the skin is extremely rough, similar to sandpaper in texture
  • They are the most fertile of all fishes, producing up to 300 million tiny eggs
  • The name ‘mola’ is derived from the Latin word for millstone because of their similar shape
Aquarist Nicholas Nicholle rescues a sunfish from dry dock

See also

Download a research paper about sunfish that appeared in the Journal of Experimental Marine Biology and Ecology: