The ocean sunfish is a huge, flattened fish that looks like a giant swimming head. It lives in open oceans worldwide and feeds mostly on jellyfish, making it an important part of ocean food webs.
Interesting facts
- Sunfish are among the heaviest bony fish in the world.
- They have no true tail; instead, a stiff, rounded flap called a clavus acts as a rudder.
- After diving into cold, deep water to feed, they bask on their side at the surface to warm up.
- Seabirds and small fish remove parasites from sunfish that visit ‘cleaning stations’.
- A young sunfish at Monterey Bay Aquarium gained almost 400 kg in about 15 months.
- Its scientific name ‘mola’ is Latin for millstone, describing its round, grey shape.
Behaviour
Sunfish swim by flapping their tall dorsal and anal fins together. They regularly dive to depths of 200–600 metres to hunt and return to the surface to warm up and get cleaned of parasites.
Breeding and young
Females release huge numbers of tiny eggs into the water. The larvae are covered in spines and grow at an astonishing rate, increasing in weight many millions of times.
Threats and conservation
Accidental capture in drift nets and longlines, collisions with boats, and plastic bags that are mistaken for jellyfish.
Where to see it
- Nusa Penida, Bali, Indonesia, from July to October (mostly the related bump-head sunfish)
- Monterey Bay, California
- Punta Vicente Roca, Galápagos
- Coasts of Cornwall, Ireland and Portugal in summer
Status source: IUCN Red List. Profile last reviewed September 2026.
