Sunfish, or mola mola, are the second‑largest bony fish in the world. Unusual in appearance, they have a flattened, almost circular body with tall dorsal and anal fins and no true tail, leading them to be described as a ‘swimming dinner‑plate’.
Over the last week their have been two sightings of them off the coast of Mwnt and Dinas Head.
A rare sunfish or mola mola was filmed off Mwnt on Sunday, June 21. (Image: Pexels/ Joerg Mangelsen)
They can grow to more than three metres long and weigh in at over a tonne.
Sunfish are widespread in temperate and tropical seas worldwide, often spending much of their time in deeper water between about 200 and 600 metres, and coming to the surface to bask and warm up.
They feed mainly on jellyfish but will also take small fish, squid and other drifting creatures.
Sunfish are still rarely seen off the coast of the UK but are drawn here to hunt, particularly barrel jellyfish in the Irish Sea.
Sightings have increased in recent years due to increasing sea temperatures and improved reporting.
Sunfish are usually spotted basking on their side on the surface of the sea. It is thought that they do this to warm up after a deep cold dive or to invite birds to remove pests from their scales.
Sea Trust charity says that when swimming at the surface, sunfish will angle their side body, as the largest surface area, toward the sun to absorb heat.
This behaviour is observed before they dive down deep into colder waters to feed.
Sunfish are unlikely to be found in cold waters, as temperatures below 10℃ can cause serious disorientation.
Sunfish reported in UK waters tend to range in size from dinner plate to dustbin lid.
Sunfish are classed as ‘vulnerable’ on the IUCN Red List, with a decreasing global population trend.
Conservation organisations in the UK echo this, noting that while they are not formally listed as endangered here, data on regional population size is limited. On a UK/European scale not enough is known about the population.
Last weekend a sunfish was spotted off Mwnt by local Steven Miles.
“I was out on my boat, just enjoying the sun etc and saw the fish on the surface,” he said.
“I had no idea what it was. I thought it was injured. I’ve never seen such an odd-looking fish.”
Steven took a video and quickly sent it t a friend who identified it as a sunfish. He then did a bit more research, learning that it is essentially a warm water fish that spends a lot of time in deep water
“After our encounter it rolled upright and shot off into the depths,” said Steven. “It was only then that I realised it was not injured. All this happened just 100 yards off Mwnt beach. “