Ocean Sunfish Facts

The ocean sunfish (Mola mola) is certainly one of the more unusual-appearing fish in the oceans. This bony fish, also known as the common mola, is famous for its enormous bulk, striking appearance, high fertility, and free moving lifestyle. Fast Facts: Ocean Sunfish Scientific Name: Mola molaCommon Name(s): Ocean sunfish, common mola, common sunfishBasic Animal Group: FishSize: 6–10 feetWeight: 2,000 poundsLifespan: 22–23 yearsDiet:  CarnivoreHabitat: Pacific, Indian, Atlantic oceans, Mediterranean and North SeasPopulation: UnknownConservation Status: Vulnerable Description The ocean sunfish is a bony fish—it has a skeleton of bone, which distinguishes it from cartilaginous fish, whose skeletons are made of cartilage. The fish doesnt have a normal-looking tail; instead, it has a lumpy appendage called a clavus, which evolved through the fusion of the fishs dorsal and anal fin rays. Despite its lack of a powerful tail, the ocean sunfish is an active and graceful swimmer, using its dorsal and anal fins to perform rapid changes in direction and horizontal movements independent of the prevailing current. It can also leap out of the water. Ocean sunfish vary in color from brown to gray to white. Some even have spots. On average, ocean sunfish weighs about 2,000 pounds and range between 6 and 10 feet across, making them the largest  bony fish  species. Female sunfish are larger than the males—all sunfish larger than 8 feet long are females. The largest ocean sunfish ever measured was nearly 11 feet across  and weighed over 5,000 pounds.   Rodrigo Friscione/Getty Images Species The word mola in its scientific name is Latin for millstone—a large  round stone used to grind grain—and the fishs name is a reference to its disc-like shape. Ocean sunfish are often referred to as common molas or simply molas. The ocean sunfish is also known as the common sunfish, as there are three other species of sunfish that live in the ocean—the slender mola (Ranzania laevis), the sharp-tailed mola (Masturus lanceolatus), and the southern ocean sunfish (Mola alexandrini). The sunfish group gets its name for the fishs characteristic behavior of lying on its side at the sea surface, seemingly basking in the sun. Habitat and Range Ocean sunfish live in tropical and temperate waters, and they can be found in the Atlantic, Pacific, and Indian Oceans as well as inlets such as the Mediterranean and North seas. They generally stay within 60–125 miles of the coastline, and they apparently migrate within their ranges. They spend the summers at higher latitudes and their winters relatively closer to the equator; their ranges typically are along about 300 miles of coastline, although one sunfish off the coast of California was mapped at traveling over 400 miles. They move during the day horizontally at rate of about 16 miles a day. They also move vertically through the day, traveling between the surface and up to 2,600 feet below, moving up and down the water column during the day and night to chase food and regulate body heat. To see an ocean sunfish, though, youll likely have to find one in the wild, because they are difficult to keep in captivity. The Monterey Bay Aquarium is the only aquarium in the U.S. to have live ocean sunfish, and the fish  are kept at only a few other aquaria, such as the Lisbon Oceanarium in Portugal and the Kaiyukan Aquarium in Japan. Diet and Behavior Ocean sunfish like to eat jellyfish and siphonophores (relatives of jellyfish); in fact, they are among the most abundant of the worlds jellyfish eaters. They also eat salps, small fish, plankton, algae, mollusks, and  brittle stars. If youre lucky enough to see an ocean sunfish in the wild, it may look like its dead. Thats because ocean sunfish are often seen lying on their sides near the ocean surface, sometimes flapping their dorsal fins. There are a few theories about why sunfish do this; they often undertake long, deep dives in cold water in search of their favorite prey,  and may use the warm sun at the surface to re-heat themselves and aid digestion. The fish may also use the warm, oxygen-rich surface water to recharge their oxygen stores. And they may visit the surface to attract seabirds from above or cleaner fish from below to clean their skin of parasites. Some sources suggest that the fish wave their fins to attract birds. From 2005 to 2008, scientists tagged 31 ocean sunfish in the North Atlantic in the first study of its kind. The tagged sunfish spent more time near the ocean surface during the night than during the day, and they spent more time in the deep when they were in warmer waters such as  the  Gulf Stream  and the  Gulf of Mexico. BarrettMacKay BarrettMacKay/Getty Images   Reproduction and Offspring Ocean sunfish in Japanese waters spawn in late summer through October and likely multiple times. Age at sexual maturity is inferred at 5–7 years of age, and they spawn an enormous number of eggs. An ocean sunfish was once found with an estimated 300 million eggs in her ovary—more than scientists have ever found in any  vertebrate  species. Although sunfish produce many eggs, the eggs are tiny and essentially scattered into the water, making their chances of survival relatively small. Once an egg is fertilized, the embryo grows into tiny spiked larvae with a tail. After hatching, the spikes and tail disappear and the baby sunfish resembles a small adult. The lifespan of an ocean sunfish is up to 23 years. Conservation Status The International Union for Conservation of Nature (IUCN) has listed the ocean sunfish as Vulnerable. Currently, sunfish are not targeted for human consumption, but they are endangered by bycatch. Reported estimates in California are that 14 percent to 61 percent of the fish caught by people seeking swordfish is sunfish; in South Africa, they make up 29 to 79 percent of the catch intended for horse mackerel, and in the Mediterranean, an astounding 70 to 95 percent of the total catch for swordfish is, in fact, ocean sunfish. The global population of sunfish is difficult to determine, since they spend so much time in deep water, although tagging has become more common. Sunfish may be a crucial part of the planets changing ecosystem under climate change: They are among the worlds most abundant eaters of jellyfish, and global warming appears to be resulting in an upsurge of jellyfish numbers. The biggest natural predators of ocean sunfish are  orcas  and  sea lions. Ocean Sunfish and Humans Despite their enormous size, ocean sunfish are harmless to humans. They move slowly and are likely more frightened of us than we are of them. Because they are not considered a good food fish in most places, their biggest threats are likely being hit by boats and being caught as bycatch in fishing gear.   Franco Banfi/Getty Images Sources Dewar, H., et al. Satellite Tracking the Worlds Largest Jelly Predator, the Ocean Sunfish, Mola Mola, in the Western Pacific. Journal of Experimental Marine Biology and Ecology 393.1 (2010): 32–42. Print.Liu, J., et al. Mola mola (errata version published in 2016). The IUCN Red List of Threatened Species: e.T190422A97667070, 2015.   404 404 404Potter, Inga F., and W. Huntting Howell. Vertical Movement and Behavior of the Ocean Sunfish, Mola Mola, in the Northwest Atlantic. Journal of Experimental Marine Biology and Ecology 396.2 (2011): 138–46. Print.Sims, David W., et al. Satellite Tracking of the Worlds Largest Bony Fish, the Ocean Sunfish (Mola Mola L.) in the North East Atlantic. Journal of Experimental Marine Biology and Ecology 370.1 (2009): 127–33. Print.Thys, Tierney M., et al. Ecology of the Ocean Sunfish, Mola Mola, in the Southern California Current System. Journal of Experimental Marine Biology and Ecology 471 (2015): 64–76. Print. 404 404 40 4