It’s feeding time for the Monterey Bay Aquarium’s new ocean sunfish, or mola mola. Senior aquarist Michael Howard walks out a 20-foot walkway extending over the middle of the million-gallon Outer Bay exhibit. He places a red-and-white striped ball on the surface, which the mola has been “target trained” to associate with a meal. Sure enough, the mola comes toward the surface with deliberate movements and bumps its nose against the ball.
Michael lies down to get closer, then reaches into a plastic dish that contains what looks like restaurant quality fare: squid, shrimp, as well as a much less appetizing but nutritious “gel” stuffed in a sausage casing. He presents each piece with a pair of tongs. It’s not quite hand-feeding, but it’s close, and it all goes down that round, gaping mouth quickly and without complaint.
A “Millstone” in the Monterey Bay
The world’s largest bony fish, molas can reach 14 feet in length and tip the scales at an SUV-like 5,000 pounds. (Monterey Bay molas reach a still-massive 1,000 pounds.) Its Latin name, fittingly, means “millstone.”
In nature, you might think that such a large fish would consume other large prey. While the mola does consume a lot of food, its primary meal is the ethereal and airy moon jelly. As you might guess, this is a little like humans eating popcorn—it takes a lot to make a meal.
The mola gets fed two to three times per day, which means that staff have to be careful not to bestow “too much love,” says Michael. Food intake is closely monitored, with total daily offerings targeting 1-2 percent of body weight. Without careful monitoring, a big fish like the mola can become even bigger. In 1998, a mola at the Aquarium grew from 57 to 880 pounds before it was successfully lifted out of the Aquarium by helicopter. The last mola reached its size limit for the exhibit and was successfully released into the bay in March 2009.
Michael is spearheading growth studies to learn more about the diet and caloric needs of this iconic fish. Aquarium staff are also involved in a tagging program to learn more about mola habitat preferences and migratory patterns. Nine molas have been tagged to date, supplying information that could be crucial to the health of the species. In California, nearly 30 percent of the catch in a swordfish boat can be molas caught by mistake—rivaling or exceeding the number of swordfish caught. They are also threatened by floating trash.
The Monterey Bay Aquarium was one of the first to successfully exhibit the species, and Michael's work is all part of the Aquarium’s efforts to unwrap the mysteries of the mola. “There’s no written recipe for this,” says Michael. “It’s one reason I really like caring for the mola—we’re always learning.”