10 fascinating Sunfish facts

Sunfish © Island Cruising NZ

1.Sunfish don't have a tail! Some people call them a 'gigantic swimming head' (which seems a bit rude). Instead of a tail their dorsal and anal fins are fused together into a rudder-like structure called a clavus. The sunfish swims by flapping its dorsal and anal fins synchronously, like oars.

2. There are four species of sunfish: common sunfish (Mola mola), slender sunfish (Ranzania laevis), sharp-tailed sunfish (Masterus lanceolutus) and southern ocean sunfish (Mola ramsayi).

3. Sunfish are the heaviest bony fish species alive today. Common sunfish weigh around a metric tonne on average. The biggest common sunfish ever caught weighed over two metric tonnes!

4. Sunfish eat jelly (but no ice cream). We think they eat jelly-like small gelatinous animals (including jellyfish) but are known to also snack on algae, crustaceans, and small fishes if the opportunity presents itself.

5. Scaly? I don't think so! Sunfish have a tough, elastic skin which is covered in mucus. Delightful.

6. Sunfish have record-breaking fertility One female was found to produce 300 million eggs at a time, the largest number of eggs ever recorded from a vertebrate.

7. No one knows where or when sunfish babies are made. Scientists don't know where sunfish spawn, although several possible areas in the Atlantic, Pacific, and Indian oceans have been identified.

8. Is it a bird? No, but it does have a beak. Sunfish mouths are fused together to form a beak, helping it to keep hold of and bite chunks out of slippery jelly-fish.

9. Playing dead: sometimes sunfish appear to be dead, floating on their side at the ocean surface. Don't worry! The sunfish (generally) aren't dead, but scientists don't know why they do this. It could help the sunfish to warm up from their deep-water dives in search of prey. Or it could be an opportunity for the sunfish to engage the services of a cleaner fish to remove the huge numbers of parasites they harbour.

10. Big? Yes. Dangerous? No. Despite their size, sunfish don't pose a threat to humans, although given the jaw muscles and teeth fused into something like an industrial bolt cutter, you don't want to go putting your fingers anywhere near the mouth. We pose more of a threat to the sunfish, mainly through the fishing industry. Although sunfish aren't good to eat, they comprise a large proportion of bycatch in fisheries in the Atlantic and Pacific oceans.

This article has been provided by the courtesy of Island Cruising NZ.