It might have floated into British waters straight off a medieval seafaring map: a beast too fabulous for reality, too disproportionate to exist. Yet on the south-western coast, when gorse daubs rocky shorelines with yellow and the sea shimmers cobalt blue, an apparition greets those looking down into the water: a fish as pale as the moon, as round and flat as a dustbin lid, lying on its side as it apparently basks in the sun.
What is a sunfish
Nothing about the ocean sunfish, or Mola mola, seems quite possible. Not its shape – it could be a model for an old-fashioned doorknocker, so circular with a large eye, open mouth and shark-like dorsal fin.
A creature of warm and temperate waters across the globe, they have acquired many local names which, when translated, signal universal bewilderment at the missing rear half of the body: “Cut Short” in the Philippines, “Swimming Head” in German.
A fish whose tail is a mere fan-like flap is not in the contest for the fastest swimmer, but slow and steady, the sunfish does travel well: one tagged individual achieved over 2,500 km in a few months.
What do sunfish eat
They do not come to Britain to be idle; they hunt prey such as the dustbin-lid jellyfish, a pale golden giant of the Irish sea. The sunfish’s throat is laced with hooked pharyngeal teeth to help it consume such slippery morsels.
Are sunfish under threat?
Sadly, they may also consume plastic bags floating in the water. Sunfish are considered an internationally vulnerable species and, like dolphins, are often caught by the more controversial forms of tuna fishing.
How big is a sunfish
This is the second-largest of all bony fish, topping 1,000kg on the scales and over three metres in length.
Those that reach the UK tend to be much smaller, but they are still round and remarkably narrow, like a two-dimensional fish that has somehow jumped off a sketchbook.
Why do sunfish sunbathe?
On good summer days in the sparkling Cornish seas, sunfish are lying on their sides at the surface, bobbing like a swimmer on a lilo. They may be warming up after a dive into deeper, colder waters; it could also be that they are inviting birds to peck away any parasites. Strange they may be, but sunfish still add to the ocean’s charm.
Where to see sunfish in the UK
Sightings are becoming ever more frequent off the Cornish coast, and you can book boat trips to catch a glimpse of this remarkable species.
Find out more
What else lurks beneath our UK waters? Check out our expert guides from jellyfish to small river fish and from seahorses to bluefin tuna.
