By Kastalia Medrano
The remarkable ability of Internet users to make a post go viral has produced a new treat: an enchanting picture of a Mola mola, or ocean sunfish, undulating just below the surface of the ocean. The image, snapped by photographer Daniel Botelho in 2010, is now making waves around Facebook.
The attention might be focused on the one image for the moment, but sunfish are worth learning about in their own right. National Geographic spoke to Dr. Tierney Thys, who in addition to being named a National Geographic Explorer, is both founder and director of the Ocean Sunfish Tagging and Research Program.
NG: Let’s start with the basics—what exactly is a sunfish?
TT: It’s the world’s heaviest bony fish. It’s in the same order as puffer fish and porcupine fish, but it’s one of the most evolutionarily derived fishes in the sea. So, it has a cranium more like what ours looks like, along with fewer vertebrae; its spinal column is actually shorter than its brain. And they’re one of the most fecund vertebrates in the world; a 4-ft female was recorded as having an estimated 300 million eggs.
Are they endangered?
It’s unknown because they’re not commercially targeted. And as adults they don’t school; younger ones will, but as adults they become loners. So we don’t really know the status of their population.
We’ve been tagging them all over the world. They’re very vulnerable to fishermen’s nets, they get caught in huge numbers [because] they spend a lot of time lying around on top of the ocean. Some of our data is on whether that’s having an impact on their population. There are inklings that it is.
Where do they live?
That’s something we’re working on right now, understanding the global population. They have a huge range. They live in all tropical and temperate oceans, up farther north than the Arctic Circle, and all the way down by Cape Town in South Africa.
Sunfish look flatter and more compact than other fish. Why is that?
The only way to understand [the sunfish] is to study its ancestry. Their design has evolved to be more like an armored tank with a stiff body as opposed to a streamlined torpedo body like other fish. They just look like big puffer fish on steroids. They use mostly their fins for propulsion as opposed to wagging their body.
Sunfish can grow to be more than 10 feet long. Are they aggressive?
They’re not dangerous to people. They will bite if you’re harassing them, but they’re actually very gentle in nature, very passive.
They look lazy, but they’re really industrious. They dive up and down as much as 40 times a day. We recorded them off the Galapagos Islands diving as deep as 1,100 meters [3,600 feet].
So they don’t munch on people?
They’re actually the world’s largest jelly-eater. And people love the sunfish, it’s a lot of people’s favorite fish. There’s poetry, folklore—you can even adopt them.