Ocean sunfish (mola)

How it lives

Mola mola dives deep to feed. Fish tracked off Japan dived to about 600 m, into water near 2°C, then rested at the surface between dives. That famous lying-on-the-side pose is often about warming up again, not only sunbathing. Sunfish have no true tail. They swim with their tall back and belly fins and steer with a rounded rudder called the clavus. A large female Mola mola was once estimated to carry about 300 million eggs, one of the highest numbers known for any animal with a backbone.

Where it goes

Sunfish are ocean travellers, but each fish writes its own route. In the northeast Atlantic, tagged Mola mola moved north in spring and summer and south in the cooler months, towards north-west Africa and the Mediterranean. In the northwest Atlantic, fish left northern waters in late summer and followed the continental shelf south. Off California, tagged fish moved between southern California and Baja California. Bump-head sunfish tagged off Taiwan swam north to Japan or south to Papua New Guinea and New Caledonia. These are single tracks, not a fixed yearly route.

Follow its journey on the map

Populations

Mola mola lives in tropical and temperate seas of every ocean, including the Mediterranean, the North Sea, the Sea of Japan and the Gulf of California. Scientists study it most around Portugal and Spain, Ireland, southern California and Baja California, and Japan. Its cousin, the bump-head sunfish, lives in Indonesia, Taiwan and Japan, Australia, New Zealand, the Galápagos and even the Azores. In Bali, the reef sunfish at Nusa Penida and Lembongan are almost all bump-head sunfish.