Heaviest bony fish
Who
Bump-head sunfish
What
2.3 tonne(s)/metric ton(s)
Where
Japan ()
When
1996

The heaviest bony fish are the sunfish (genus Mola), with adults obtaining an average length of 1.8 metres (6 feet) and weighing around 1,000 kilograms (2,200 pounds). The heaviest specimen on record is a bump-head sunfish (Mola alexandrini) caught off Kamogawa, Chiba, Japan, in 1996; it weighed 2,300 kilograms (5,070 pounds) and measured 2.72 metres (8 feet 10 inches) long.

The superlative specimen was previously thought to be an ocean sunfish (Mola mola), but this was refuted in a study by Hiroshima University, the University of Tokyo (both Japan) and Murdoch University (Australia) published in the journal Ichthyological Research on 5 December 2017.

The same study also contests that the bump-head sunfish (Mola alexandrini) is synonymous with the southern sunfish (Mola ramsayi).

An even longer sunfish – this time an ocean, or common, sunfish Mola mola – was found floating off Whangarei Heads in New Zealand in 2006, with a total length of 3.3 metres (10 feet 9.9 inches); its weight was estimated at 2,200–2,300 kilograms (4,850–5,070 pounds). Further, in 2004, a female sunfish caught off Aji Island, Miyagi Prefecture, Japan, measured 3.32 metres (10 feet 10.7 inches) long, but she was not weighed.

The name Mola comes from the Latin meaning millstone. Sunfish are found in all oceans in tropical or temperate climates and feed on zooplankton, small fishes and algae.