Sunfish - Mark Harris

Mola mola, so good to see

3 minute read

Tom "The Blowfish" Hird Ocean Ambassador

Tom 'The Blowfish' Hird

9 Aug 2022

In the summer edition of our members magazine, Ocean Ambassador Tom ‘The Blowfish’ Hird wrote a fascinating piece about the ocean sunfish. Dive into his article to find out all about the mola mola.

The ocean is home to the beautiful and the deadly, the elegant and the terrifying, the massive and the delicate. It’s a unique and often indescribable mix of wonder and awe. Then there’s the sunfish... and, well... I’m sure he’s got a wonderful personality.

The ocean sunfish, or Mola mola, is a regular visitor to our summer coastlines. While not the type of animal you’d see floundering in a rock pool when the tide has gone out, this odd fish often greets boaters, paddleboarders and kayakers in inshore waters during summer. Sunfish are found in temperate to tropical oceans in both hemispheres, and while they are known for diving and hunting in deep, dark waters, they are dedicated heliophiles, or ‘sun-lovers’. In fact, the common name of sunfish doesn’t just come from its chunky figure but also its habit of lying in the warm surface waters working on its tan.

The heaviest bony fish in the ocean

Now, you may think I’m being cruel to the sunfish but I love them very, very much. It’s just that one odd fish recognises another. And I see a real winner in that category here. The sunfish would best be described as a manhole cover with two cricket bats for fins. This huge flat-sided fish has a heavily reduced tail and overly extended dorsal and ventral fins. At the front end you have a mouth like a vacuum cleaner, evolved to suck up squid, small fish, jellyfish, salps and other deep-sea softies in mere seconds. It’s so effective that the sunfish ranks as the heaviest bony fish in the ocean, with a large specimen weighing more than two tons and measuring four metres from fin to fin.

Down below 200m is where the sunfish hunts shoals of squid, shrimplike crustaceans and colonies of slow-swimming jellies, but studies have shown that if exposed to temperatures below 10°C for extended periods of time, the sunfish will start to fade, become disorientated and die. It is these freezing feeding trips that result in the sunfish displaying its famous, name-defining behaviour.

To recover from a dive and prepare for the next one, sunfish lie at the very surface of the ocean, flat on one side, absorbing the sun’s rays. This basking behaviour not only brings the core temperature of the sunfish back up to tolerable levels, but also allows for a much needed clean.

Surface clean

Spending extended periods at depth brings you into contact with many creatures, not just predators and prey but also parasites. Sunfish have a much-reduced layer of scales, to the point where they are just tiny, hardened pimples embedded in a thick flesh. This leaves the sunfish without an armoured shell, making it an easy target for parasites which can burrow through the skin and feed on the juices within. By basking at the surface, exposing its pale circular side to the sun, the sunfish signals that an all-you-can-eat parasite buffet is open for passing seabirds. These feathered friends can then descend on the sunfish and, with sharp beaks and keen eyes, winkle out even the most stubborn of blood-sucking hitchhikers.

Sunfish - peter bardsley

Credit: Peter Bardsley

Sunfish and climate change

We are quite lucky here in the UK to see sunfish at all. The water is just on the borderline for suitable sunbathing. It is thanks to the Gulf Stream and its tropical origins that boost our temperatures up just high enough to enable us to welcome regular summer visitors such as the sunfish. It’s likely that we may see more and more sunfish venturing further up the British Isles as ocean temperatures continue to rise.

However, this shouldn’t be seen as some hidden silver lining to climate change; while surface temperatures rise, the effects on the deep ocean are unknown. Certainly, studies would suggest that warmer surface waters results in reduced deep ocean circulation so fewer nutrients are transported into the depths, and less oxygen too. Considering this is the feeding ground for the sunfish, along with many other incredible species, a collapse of the deep ocean ecosystems would be catastrophic.

About ‘The Blowfish’

Our Ocean Ambassador, Tom ‘The Blowfish’ Hird, has wowed audiences of all ages around the country as the world’s ONLY heavy metal marine biologist with his science communication shows. He’s the author of Blowfish’s Oceanopedia – 291 Extraordinary Things You Didn’t Know About The Sea and is a wildlife expert appearing on CBBC, ITV, BBC, CITV, Discovery and Channel 4. He’s also presented two series of the BBC Worldwide production, Fishing Impossible which is shown across the globe. Tom hosted our online AGMs in 2020 and 2021.