Meet the new giant sunfish that has evaded scientists for centuries

The massive ocean sunfish — an odd-looking fish with a flat, rigid, tailless body — is not only the world’s largest bony fish, but also one of the most elusive fishes in the world.

Now, for the first time in 130 years, scientists have identified and described a new species of this giant fish that they say has been “hiding in plain sight for centuries”. Lead author Marianne Nyegaard of the Murdoch University in Australia and her colleagues have named the new species the Hoodwinker sunfish or Mola tecta (derived from the Latin word tectus meaning disguised or hidden).

Spotting the sunfish is difficult because it lives a solitary life, diving hundreds of meters to feed and occurring in parts of the ocean where people don’t tend to go. The fish sometimes gets caught on fishing gear as bycatch or gets stranded on the beach, when it can be photographed or sampled.

As part of her PhD research, Nyegaard analyzed DNA from more than 150 skin samples of sunfish and found that the samples pointed towards four distinct species. But only three species — Masturus lanceolatus, Mola mola, and Mola ramsayi — had been previously described, the scientists report in a new study published in Zoological Journal of the Linnean Society. The fourth one had not been recorded yet. A Japanese research team had found similar genetic evidence of an unknown sunfish species in Australian waters some ten years ago.

To find out what this new species might look like, Nyegaard started scouring social media for pictures of sunfish and built a network of people across Australia and New Zealand who could alert her whenever a sunfish was observed. She hit the jackpot in 2014 when four sunfish were stranded on the same beach in New Zealand.

“I flew down to Christchurch, landed at night and drove out on to the beach,” Nyegaard wrote in the Conversation. “I saw my first hoodwinker sunfish in the headlights of the car – it was incredibly exciting. This changed everything, because now we knew what we were looking for.”

Over the next few years, Nyegaard and her colleagues from Hiroshima University, the University of Tokyo, the Museum of New Zealand Te Papa Tongarewa, and the University of Otago, collected and examined 27 specimens of the fish and reviewed old photos and museum collections to confirm and describe the new Hoodwinker sunfish.

“This new species is the first addition to the Mola genus in 130 years,” Nyegaard said in a statement. “The process we had to go through to confirm its new species status included consulting publications from as far back as the 1500s, some of which also included descriptions of mermen and fantastical sea monsters. We retraced the steps of early naturalists and taxonomists to understand how such a large fish could have evaded discovery all this time. Overall we felt science had been repeatedly tricked by this cheeky species, which is why we named it the Hoodwinker.”

The Hoodwinker sunfish can weigh up to two metric tonnes and can grow up to 2.5 meters (over eight feet), the team estimates. The fish’s slim, sleek body doesn’t change much between juveniles and adults and it doesn’t develop lumps and bumps during its growth like other sunfish species.

The team is yet to determine the Hoodwinker’s range, but they have found the fish around New Zealand, off Tasmania, South Australia, Victoria and New South Wales (Australia), South Africa and southern Chile, suggesting that the species might be found lurking in the colder parts of the Southern Hemisphere.

Citation:

• Nyegaard M, et al (2017). Hiding in broad daylight: molecular and morphological data reveal a new ocean sunfish species (Tetraodontiformes: Molidae) that has eluded recognition. DOI: https://doi.org/10.1093/zoolinnean/zlx040