Mola may not be a household name, but the various species of this genus of sunfish are found in temperate and tropical seas all over the world and can reach nearly 11 feet (3.3 meters) in length and weigh up to 5,070 lbs (2,300 kg).
To live large, these marine giants grow fast: in captivity, young sunfish can pack on more than 800 pounds in just over a year. Mola mola school as adolescents and as adults become loners, which makes them less susceptible to commercial fishing.
This animation of the Mola mola—featured life-sized in the exhibition Unseen Oceans—conveys their staggering size and placid temperament. (Mola mola appears at 1:25 in the video below.)
Size gives the Mola mola several advantages. Females produce enormous numbers of eggs: one 4-foot (1.2 meter-long) female was estimated to be carrying 300 million eggs. The Mola mola also has a broad thermal range, from 36°F to 86°F, allowing it to dive more than 3,000 feet deep (914 meters).
There is slim preliminary evidence that the ocean sunfish may be able to tolerate low oxygen levels, but that would be a boon, as such conditions are among a growing list of concerns in today’s oceans, along with human pollution and global sea temperature rise.
As adults, their appetite for jellyfish means ocean sunfish are helping combat another modern marine threat. “As we overfish the ocean, in some regions, jellies can move in to fill those open niches,” says marine biologist Tierney Thys, who has tracked ocean sunfishes all over the globe. “As these local jelly populations increase, we need to keep our populations of jelly eaters—like the Mola mola—intact.”
Visitors can see life-sized animations of the Mola mola and other marine giants on a 180-degree screen in Unseen Oceans, which is free for Members.