Latin name

Mola mola

Other names

Headfish, moonfish; Danish/Swedish: klumpfisk; Dutch: maanvis; Finnish: m hk kala; French: môle commun, poisson-lune; German: mondfisch; Greek: fegaró psaro; Icelandic: tunglfiskur; Italian: pesce luna; Norwegian: månefisk; Polish: samoglów; Portuguese: lua, peixe-lua; Spanish: mola, pez cabeza, pez luna, pez sol; Turkish: pervane.

Identification

The short, strongly laterally compressed body is disk-shaped. Thick skin is covered with small bony tubercles. Dorsal and anal fins high opposed, moved far backward, merged with the reduced caudal fin. Teeth on the jaws merge with each other to form plates, undivided in front. Swim bladder is absent in adults. The oceanic sunfish is characterized by a greatly reduced caudal fin, which is gently curved and robust. It also has long dorsal and anal fins, which it uses to swim by paddling. It has no dorsal and pelvic fins and is a dark brownish gray or gray-blue color. The fish has no scales, a small terminal mouth, and an underdeveloped skeleton.

Distribution

The oceanic sunfish is distributed in temperate and warm waters of the epipelagic World Ocean, in the eastern Pacific Ocean from British Columbia to Peru and Chile. In the western Atlantic Ocean, it is found from Canada to northern South America. In the Southern Hemisphere, this fork reaches the Cape of Good Hope and the coast of Chile. In the far eastern seas, it occurs occasionally in summer in the northern part of the Sea of Japan and near the southern islands of the Great Kuril Ridge.

Habitat

An epipelagic oceanic planktonic form. Often drifting near the surface, lying on their sides, oceanic sunfish may also swim vertically and close to the surface with their dorsal fins protruding above the water. In cold water, they are nimble.

Size

Ocean sunfish can grow up to 10 feet long and 11 feet tall (including dorsal and anal fins) and weigh up to 4,400 pounds. A fish 5.5 meters long has been caught off the Atlantic coast of America.

Life history and Behavior

Female ocean sunfish are record holders for fecundity among vertebrates: a single individual can spawn up to 300 million eggs (a record of 847 million has been recorded). The eggs are pelagic, about 1.3 mm (0.05 inches) in size. Spawning occurs in tropical and temperate waters; in Japan, it occurs from August to October. The fish show no parental care.

The larvae bear no resemblance to adult individuals — they are covered with spines and have a rounded shape. Their tail does not develop; instead, a clavus (pseudotail — a rudder-like structure) is formed. Growth can be very rapid: in the Monterey Bay Aquarium, one individual gained 364 kg (802 lbs) in 14 months. Lifespan in the wild is not precisely known; in captivity, it is up to 10+ years.

Contrary to appearances, these fish swim actively, covering up to 26 km (16 miles) per day at a speed of about 3.2 km/h (2 mph). They are capable of significant horizontal migrations over hundreds and thousands of kilometers. They regularly dive to depths of over 500 meters (1,640 feet), following their prey. They perform daily vertical migrations. Basking (lying on the surface) helps them warm up after cold dives, rid themselves of parasites, and possibly expel gases from the intestines.

Food and feeding habits

Oceanic sunfish feed on zooplankton, eel larvae, and small deep-sea fish, as well as jellyfish, crustaceans, mollusks, and brittle stars.

Reproduction

Fertility, up to 300 million eggs. The eggs are pelagic. In the Pacific Ocean, larvae have been recorded between 140°E. - 140°W and 10-30°N, as well as around the Society and Easter Islands, in the Indian Ocean - 10°S, 90°E. Breeding areas are only in the central parts of subtropical circles.

Interesting facts

Ocean sunfish are not good swimmers at all. Other poor swimmers include pufferfish and boxfish. They cannot bend their bodies when they move, so they only swim with the help of their fins. The seahorse does not like to move in vain. It hooks its tail on some aquatic plant and catches its prey. When it rises to the surface, it swims in a spiral - it bends its tail stalk and swims fast and furiously with its dorsal and pectoral fins. 

Ocean sunfish larvae begin life at a size of only about 2 mm (0.08 inches). Their large eyes, with well-developed optics, allow them to effectively track and catch microscopic prey, which is critical for rapid growth. Although their adult relatives feed on jellyfish, the diet of the larvae consists of smaller organisms. At an early age, the larvae are extremely vulnerable. Good vision gives them the ability to detect approaching predators in time and evade them, increasing their chances of survival. The open ocean, where these larvae live, has no landmarks. Large eyes help them use celestial cues (position of the sun, polarized light) for navigation and finding suitable habitats.