05 Mar Nusa Penida is now home to the world’s largest bony fish – the Mola Alexandrini (previously known as Mola ramsayi)

You would think a fish as large as the Mola mola (up to 3 meters long and weighing 2300 kilograms) could not be mistaken. But in fact, we have been misidentifying this ocean giant for years!

The ocean sunfish (Mola mola) is listed in Guinness World Records as the world’s heaviest bony fish, however this has been a Mola alexandrini all along!

A research paper published in January 2018 was conducted by Japanese fish experts examining accounts of sunfish sightings and captures going back 500 years. They discovered the world’s heaviest bony fish ever caught is a Mola alexandrini – or a bump-head sunfish, and not, as originally thought, a member of the more commonly known Mola mola species.

The paper explores the three known Mola species: Mola mola, Mola ramsayi and the rare Mola tecta. They then found that Mola ramsayi is actually synonymous with Mola alexandrini.

Thus, Mola ramsayi which was thought to be the species we commonly see at Nusa Penida is actually a Mola alexandrini and is considered the world’s largest bony fish! This species has a large swelling on its forehead, hence its common name: the bump-head sunfish. It also has a giveaway bump on its chin and a differently shaped tail which makes it easier to differentiate from the other two mola species. One of the researches Etsuro Sawai at Hiroshima University in Japan argues that Mola alexandrini is the same as Mola ramsayi, and that Mola ramsayi (the Mola we see at Nusa Penida) should now be called Mola alexandrini because that name was used first.