Sunfish live on a diet consisting mainly of jellyfish, but because this diet is nutritionally poor, they consume large amounts to develop and maintain their great bulk. Females of the species can produce more eggs than any other known vertebrate. Sunfish fry resemble miniature pufferfish, with large pectoral fins, a tail fin, and body spines uncharacteristic of adult sunfish.
Adult sunfish are vulnerable to few natural predators, but sea lions, killer whales, and sharks will consume them. Among humans, sunfish are considered a delicacy in some parts of the world, including Japan, Korea, and Taiwan. In the EU, regulations ban the sale of fish and fishery products derived of the Molidae family. Sunfish are frequently caught in gillnets.
A member of the order Tetraodontiformes, which also includes pufferfish, porcupinefish, and filefish, the sunfish shares many traits common to members of this order. The ocean sunfish, Mola mola, is the type species of the genus.