Species Focus; Ocean sunfish - mola mola

Some weigh in at over two tonnes.

But as enormous as the ocean sunfish is, it only seems to resemble half a fish, with a large head, no noticeable body, and small fins. Many cultures’ names for the animal refer to these features of it, including the German term Schwimmer Kopf, meaning “swimming head”.

Ocean sunfish are true to their name in that they often sunbathe at the surface, largely to warm up after foraging dives in colder, deeper waters. Here the lazy motion of their large upright dorsal fin can often be mistaken for sharks cruising the surface.
Mola often become so infested with external parasites, such as copepods, that they are regularly seen at fish cleaning stations. They even allow seabirds to pick off the parasites at the surface. Even more remarkable are their full breaches, where the fish completely clears the water in a presumed attempt to dislodge its parasites. The power to leave the water in this manner is a sure indication of how fast they can swim, not bad for a two-ton “head” with only small dorsal and anal fins for propulsion.

The sunfish’ four fused teeth are an indication of their family relations; they are in the family Tetradontidae, which includes pufferfish and porcupinefish. In fact, their larvae don’t resemble adult sunfish at all but appear very similar to pufferfish with spines, large pectoral fins and a tail. The tail subsequently stops growing and folds in on itself to become a basic rudder.

Sunfish dine predominantly on jellyfish and salps which they consume with their small beak-like mouth and their very low nutrition rate means huge quantities have to be consumed. Unfortunately, due to the close resemblance of jellyfish to plastic, sunfish often also consume large amounts of plastic materials causing them to either suffocate or block up their insides.

Interesting Facts; Ocean sunfish - mola mola

1. The world’s heaviest bony fish, with some weighing over two tonnes.
2. Found worldwide in temperate and tropical waters.
3. Feeds on jellyfish and salps.
4. Lay more eggs than any other vertebrate animal, up to 300,000,000 eggs at one time.
5. Mola means “millstone” in latin, referring to their grey, round shape and rough texture.
6. Predated on by sea lions, orcas and sharks.
7. Closely related to pufferfish and porcupinefish.
8. Utilises seabirds to remove parasites at the surface