Bump-head Sunfish

Mola alexandrini

The bump-head sunfish is one of the two giant ocean sunfishes of the southern hemisphere and the heaviest bony fish ever weighed, at well over two tonnes and up to about three metres long. Adults are deep-bodied and abruptly truncated behind, so the animal reads as a swimming head, with a bony bump on the snout and another above the eyes in large individuals. It ranges through open ocean but rises from cool deep water to visit cleaning stations on coastal reefs, where bannerfish and other cleaner species strip parasites from its skin — the behaviour that makes it reliably divable at Nusa Penida in Bali and around southern Australia and New Zealand. It feeds mainly on gelatinous plankton such as jellyfish and salps.