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Fact File: Ocean Sunfish (Mola mola)

The Ocean sunfish (the amazingly named Mola mola) is one of the heaviest known bony fishes in the world, weighing in anywhere between 250kg to a ton!  We were lucky enough to have one pay us a visit recently.

Large and laterally flat, sunfish often look a bit like a large grey dustbin lid floating in the water.  They live across a large range of habitats, from tropical to temperate (down to a temperature of around 10 Celcius) in every ocean of the world and feed at various depths.  The south west coast of the UK is about the limit of its range though because of the lower average sea temperature here, so they are a rare sight around here.  When they are found in waters they often bask at the surface on their side, exposing their large surface areas to the sun to help them warm up, with large sunfish sometimes causing a hazard to boats.  When they’re feeling particularly energetic they can even breach, and jump out of the water!  It was once thought that they mainly ate jellyfish, which would explain their visits to UK coastal waters in the early summer months, but have since been found to have a general diet that includes small fish, squid and crustaceans.

It’s always nice to see such amazing examples of the marine life that lives in and visits the seas off Cornwall, especially when it’s such a rare, large, and docile creature as the Ocean Sunfish.  This one swam over to us during a 1:1 guided swim from Port Gaverne to Port Isaac and back, swam around us a few times to check out what we were, and then carried on its way.