When a rare, giant tropical sunfish found only south of the equator washed up on southern California’s temperate coast, researchers were stumped.

The hoodwinker sunfish (Mola tecta) was only first described by sunfish expert Marianne Nyegaard in 2017 in the Zoological Journal of the Linnean Society, making it the first addition to the Mola genus in 125 years. Until last month, it had never been observed outside of the Southern Hemisphere.

“I literally, nearly fell off my chair (which I was already sitting on the edge of!),” said Nyegaard in a statement.

Measuring 2 meters (7 feet) long and weighing up to 2 tons, the hoodwinker was at first mistaken as a Mola mola sunfish, which is known for frequenting the Santa Barbara Channel. After hearing of the washed-up fish, conservation specialist Jessica Nielsen took photos and preliminary measurements of the specimen and posted them on a Facebook page. Thomas Turner, an associate professor of ecology, evolution, and marine biology, saw the photos and took his family to the beach. He then posted additional images to iNaturalist, an online community for citizen scientists.

This hoodwinker sunfish, or Mola tecta, a species never before documented in the Northern Hemisphere, washed up at Sands Beach in February 2019. Thomas Turner/UC Santa Barbara

That’s when fish scientists from down under caught wind of the Mola mystery. Nyegaard teamed up with ichthyologist Ralph Foster. Together, the duo initially thought the fish could be a hoodwinker but were reluctant to identify it as such because the photos were too pixelated to be sure. Additionally, the images posted didn’t show the clavus – a hoodwinker's defining characteristic. Not to mention, the fish was far out of its usual range. From across different corners of the world, the four scientists were able to solve the fishy conundrum. The California scientists took measurements, more detailed photos, and tissue samples for DNA analysis in order to confirm that the fish was, in fact, a hoodwinker.

“This is certainly the most remarkable organism I have seen wash up on the beach in my four years at the reserve,” said Nielsen. “It really was exciting to collect the photos and samples knowing that it could potentially be such an extraordinary sighting.

“Mola tecta was just recently discovered so there is still so much to learn about this species. I’m so glad that we could help these researchers make the final definitive ID."

It’s unclear how the hoodwinker wound up so far out of its southern range, but the team of scientists say that identification is the first step in learning more about this elusive species.

Jessica Nielsen, a conservation specialist at Coal Oil Point Reserve, takes tissue samples from the hoodwinker sunfish that washed up on Sands Beach in February 2019. Thomas Turner/UC Santa Barbara