Ocean sunfish (Mola mola) in Cornwall

Also known as a head fish.

Mola actually means a millstone, a name which describes the shape of this large rounded fish.  Its skin is thick and leathery, varying in colour from grey to blackish with silvery reflections, and it often swims in an upright position at the surface, being easily noticeable by its distinctive, very tall dorsal fin; the anal fin is the same length and it swims by using both fins in a sculling movement.  Sometimes it swims or rests whilst lying on its side at the surface.  There are various theories to explain this behaviour: is it regulating its temperature?; or attracting seabirds to remove parasites: (gulls have been observed actually pecking at these fish whilst they make no attempt to swim away)?; is it sickly?; or is it affected by comparatively cold waters?  Observers of this behaviour off the Cornish coast have found that an individual will allow a close encounter from a boat and then suddenly shoot away at a good speed. 

Sunfish in Kennack Bay
photograph Colin Speedie

Those found around the British coast can reach nearly two metres in length, but they can grow considerably larger.   In the tropics, huge sunfish are found and it is reported that the children there often climb up onto them and run across them.  

They are frequent visitors around Cornwall during the summer months and, fortunately for the sunfish, they are not considered good eating or we would see fewer.  In fact there is some evidence that they are increasing in numbers and appearing earlier in the year, so all records are needed.

Stella Turk

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