Ocean sunfish

Ocean sunfish

Overview
The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish
Osteichthyes
Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...

 in the world. It has an average adult weight of 1000 kg (2,204.6 lb). The species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 is native to tropical
Tropical fish
Tropical fish include fish found in tropical environments around the world, including both freshwater and salt water species.Tropical fish are popular as aquarium fish, due to their often bright coloration...

 and temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

 and ventral fins are extended.

Sunfish live on a diet that consists mainly of jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

, but because this diet is nutritionally poor, they consume large amounts in order to develop and maintain their great bulk.
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Encyclopedia
The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish
Osteichthyes
Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...

 in the world. It has an average adult weight of 1000 kg (2,204.6 lb). The species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 is native to tropical
Tropical fish
Tropical fish include fish found in tropical environments around the world, including both freshwater and salt water species.Tropical fish are popular as aquarium fish, due to their often bright coloration...

 and temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

 and ventral fins are extended.

Sunfish live on a diet that consists mainly of jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

, but because this diet is nutritionally poor, they consume large amounts in order to develop and maintain their great bulk. Females of the species can produce more eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

 than any other known vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

. Sunfish fry resemble miniature pufferfish
Pufferfish
Tetraodontidae is a family of primarily marine and estuarine fish of the Tetraodontiformes order. The family includes many familiar species which are variously called pufferfish, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, toadies, honey toads, sugar toads, and sea squab...

, with large pectoral fins, a tail fin and body spines uncharacteristic of adult sunfish.

Adult sunfish are vulnerable to few natural predators, but sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...

s, orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...

s and shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s will consume them. Among humans, sunfish are considered a delicacy in some parts of the world, including Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, the Korean peninsula
Korean Peninsula
The Korean Peninsula is a peninsula in East Asia. It extends southwards for about 684 miles from continental Asia into the Pacific Ocean and is surrounded by the Sea of Japan to the south, and the Yellow Sea to the west, the Korea Strait connecting the first two bodies of water.Until the end of...

 and Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...

. In the EU, regulations ban the sale of fish and fishery products derived of the Molidae family. Sunfish are frequently, though accidentally, caught in gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...

s, and are also vulnerable to harm or death from encounters with floating trash, such as plastic bags.

A member of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Tetraodontiformes
Tetraodontiformes
The Tetraodontiformes are an order of highly derived ray-finned fish, also called the Plectognathi. Sometimes these are classified as a suborder of the Perciformes...

, which also includes pufferfish
Pufferfish
Tetraodontidae is a family of primarily marine and estuarine fish of the Tetraodontiformes order. The family includes many familiar species which are variously called pufferfish, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, toadies, honey toads, sugar toads, and sea squab...

, porcupinefish
Porcupinefish
Porcupinefish are fish of the family Diodontidae, , also commonly called blowfish ....

 and filefish
Filefish
Filefish are tropical to subtropical tetraodontiform marine fish of the diverse family Monacanthidae. Found in the Atlantic, Pacific and Indian Oceans, the filefish family contains approximately 107 species in 26 genera...

, the sunfish shares many traits common to members of this order. It was originally classified as Tetraodon
Tetraodon
Tetraodon is the largest genus in the pufferfish family . Its 23 members have a wide distribution, from Africa to Southeast Asia...

 mola
under the pufferfish genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, but it has since been given its own genus, Mola
Mola (genus)
Mola is a genus of the family Molidae. It includes two species, the ocean sunfish, Mola mola, and the Southern Ocean sunfish, Mola ramsayi....

, with two species under it. The ocean sunfish, Mola mola, is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 of the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

.

Naming and taxonomy



Many of the sunfish's various names allude to its flattened shape. Its specific name, mola, is Latin for "millstone", which the fish resembles because of its grey colour, rough texture, and rounded body. Its common English name, sunfish, refers to the animal's habit of sunbathing at the surface of the water. The Dutch-, Portuguese-, French-, Catalan-, Spanish-, Italian-, Russian- and German-language names, respectively maanvis, peixe lua, poisson lune, peix lluna, pez luna, pesce luna, рыба-луна and Mondfisch, mean "moon fish", in reference to its rounded shape. In German, the fish is also known as Schwimmender Kopf, or "swimming head". In Polish it is named samogłów, meaning "head alone", because it has no true tail. The Chinese translation of its academic name is fan-che yu, meaning "toppled car fish".
The ocean sunfish has various superseded binomial
Binomial nomenclature
Binomial nomenclature is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages...

 synonyms, and was originally classified in the pufferfish genus, as Tetraodon
Tetraodon
Tetraodon is the largest genus in the pufferfish family . Its 23 members have a wide distribution, from Africa to Southeast Asia...

 mola
.
It is now placed in its own genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, Mola, with two species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

: Mola mola and Mola ramsayi
Mola ramsayi
Mola ramsayi, known commonly as the southern ocean sunfish or southern sunfish, is a fish belonging to the family Molidae. It is closely related to its cogener, the large Mola mola, and is found in the Southern Hemisphere.-Description:...

. The ocean sunfish, Mola mola, is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 of the genus.

The Mola genus belongs to the Molidae
Molidae
Molidae is the family of the molas or ocean sunfishes, unique fish whose bodies come to an end just behind the dorsal and anal fins, giving them a "half-a-fish" appearance...

 family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

. This family comprise 3 genera: Masturus, Mola
Mola (genus)
Mola is a genus of the family Molidae. It includes two species, the ocean sunfish, Mola mola, and the Southern Ocean sunfish, Mola ramsayi....

and Ranzania
Slender sunfish
The Slender sunfish, Ranzania laevis, is a mola of the family Molidae, the only member of the genus Ranzania, found globally in tropical and temperate seas. Its length is up to 1 m.-References:...

. The common name "sunfish" without qualifier is used to describe the Molidae marine
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

 family as well as the freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 sunfishes in the family Centrarchidae
Centrarchidae
The sunfishes are a family of freshwater ray-finned fish belonging to the order Perciformes. The type genus is Centrarchus . The family's 27 species includes many fishes familiar to North Americans, including the rock bass, largemouth bass, bluegill, pumpkinseed, and crappies...

 which are unrelated to Molidae. On the other hand, the name "ocean sunfish" and "mola" refer only to the family Molidae.

The Molidae family belongs to the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Tetraodontiformes
Tetraodontiformes
The Tetraodontiformes are an order of highly derived ray-finned fish, also called the Plectognathi. Sometimes these are classified as a suborder of the Perciformes...

, which includes pufferfish
Pufferfish
Tetraodontidae is a family of primarily marine and estuarine fish of the Tetraodontiformes order. The family includes many familiar species which are variously called pufferfish, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, toadies, honey toads, sugar toads, and sea squab...

, porcupinefish
Porcupinefish
Porcupinefish are fish of the family Diodontidae, , also commonly called blowfish ....

 and filefish
Filefish
Filefish are tropical to subtropical tetraodontiform marine fish of the diverse family Monacanthidae. Found in the Atlantic, Pacific and Indian Oceans, the filefish family contains approximately 107 species in 26 genera...

. It shares many traits common to members of this order, including the four fused teeth that form the characteristic beak and give the order its name (tetra=four, odous=tooth, and forma=shape). Indeed, sunfish larvae resemble spiky pufferfish more than they resemble adult molas.

Description



The caudal fin of the ocean sunfish is replaced by a rounded clavus, creating the body's distinct truncated shape. The body is flattened laterally, giving it a long oval shape when seen head-on. The pectoral fins are small and fan-shaped, while the dorsal fin and the anal fin are lengthened, often making the fish as tall as it is long. Specimens up to 3.2 m (10.5 ft) in height have been recorded.

The mature ocean sunfish has an average length of 1.8 m (5.9 ft), a fin-to-fin length of 2.5 m (8.2 ft) and an average weight of 1000 kg (2,204.6 lb),
although individuals up to 3.3 m (10.8 ft) in length
4.2 m (13.8 ft) across the fins and weighing up to 2300 kg (5,070.6 lb)
have been observed.

The spinal column of M. mola contains fewer vertebrae and is shorter in relation to the body than that of any other fish.
The spinal cord of a specimen measuring 2.1 m (6.9 ft) in length is under 25 mm (0.984251968503937 in) long.
Although the sunfish descended from bony ancestors
Osteichthyes
Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...

, its skeleton contains largely cartilaginous
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 tissues, which are lighter than bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

, allowing it to grow to sizes impractical for other bony fishes.

The sunfish lacks a swim bladder. Some sources indicate that the internal organs contain a concentrated neurotoxin
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

, tetrodotoxin
Tetrodotoxin
Tetrodotoxin, also known as "tetrodox" and frequently abbreviated as TTX, sometimes colloquially referred to as "zombie powder" by those who practice Vodou, is a potent neurotoxin with no known antidote. There have been successful tests of a possible antidote in mice, but further tests must be...

, like the organs of other poisonous tetraodontiformes, while others dispute this claim.

Fins


In the course of its evolution, the caudal fin (tail) of the sunfish disappeared, to be replaced by a lumpy pseudo-tail, the clavus. This structure is formed by the convergence of the dorsal and anal fins.
The smooth-denticled clavus retains twelve fin rays, and terminates in a number of rounded ossicles.
Without a true tail to provide thrust for forward motion and equipped with only small pectoral fins, Mola mola relies on its long, thin dorsal and anal fins for propulsion, driving itself forward by moving these fins from side to side.

Ocean sunfish often swim near the surface, and their protruding dorsal fins are sometimes mistaken for those of shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s. However, the two can be distinguished by the motion of the fin. Sharks, like most fish, swim by moving the tail sideways while keeping the dorsal fin stationary. The sunfish, on the other hand, swings its dorsal fin and anal fin in a characteristic sculling motion which can be used to identify it.

Skin


Adult sunfish range from brown to silvery-gray or white, with a variety of mottled skin patterns; some of these patterns may be region-specific. Colouration is often darker on the dorsal surface, fading to a lighter shade ventrally as a form of counter-shading camouflage. Mola mola also exhibits the ability to vary skin colouration from light to dark, especially when under attack. The skin, which contains large amounts of reticulated collagen, can be up to 3 in (7.6 cm) thick on the ventral surface, and is covered by denticles and a layer of mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

 instead of scales
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...

. The skin on the clavus is smoother than that on the body, where it can be as rough as sandpaper.

More than 40 species of parasites may reside on the skin and internally, motivating the fish to seek relief in a number of ways.
In temperate regions, drifting kelp fields harbour cleaner wrasse
Cleaner fish
Cleaner fish are fish that provide a service to other fish species by removing dead skin and ectoparasites. This is an example of mutualism, an ecological interaction that benefits both parties involved. A wide variety of fishes have been observed to display cleaning behaviors including wrasses,...

s and other fish which remove parasites from the skin of visiting sunfish. In the tropics, the mola solicits cleaning help from reef fishes. By basking on its side at the surface, the sunfish also allows seabirds to feed on parasites from its skin. Sunfish have been reported to breach, clearing the surface by more than three body lengths, possibly as another effort to dislodge parasites.

Range and behavior


Ocean sunfish are native to the temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...

 and tropical
Tropical fish
Tropical fish include fish found in tropical environments around the world, including both freshwater and salt water species.Tropical fish are popular as aquarium fish, due to their often bright coloration...

 waters of every ocean in the world. Mola genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...

s appear to vary widely between the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 and Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

, but genetic differences between individuals in the northern
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...

 and southern hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

s are minimal.

Although early research suggested that sunfish moved around mainly by drifting with ocean currents, individuals have been recorded swimming 26 km in a day, at a top speed of 3.2 km/h.
Sunfish are pelagic and swim at depths of up to 600 m (1,968.5 ft). Contrary to the general perception that sunfish spend much of their time basking at the surface, research suggests that adult M. mola actually spend a large portion of their lives submerged at depths greater than 200 m (656.2 ft), occupying both the epipelagic and mesopelagic
Mesopelagic
The mesopelagic is that part of the pelagic zone that extends from a depth of 200 to 1000 metres below the ocean surface. It lies between the photic epipelagic above and the aphotic bathypelagic below, where there is no light at all...

 zones.

Sunfish are most often found in water warmer than 10 °C (50 °F); prolonged periods spent in water at temperatures of 12 °C (53.6 °F) or lower can lead to disorientation and eventual death. Researchers theorize that surface basking behaviour, in which a sunfish swims on its side, presenting its largest profile to the sun, may be a method of "thermally recharging" following dives into deeper, colder water.
Others point to sightings of the fish in colder waters outside of its usual habitat, such as those southwest of England, as evidence of increasing marine temperatures.

Sunfish are usually found alone, but occasionally in pairs or in large groups while being cleaned. They swim primarily in open waters, but are sometimes seen near kelp beds taking advantage of resident populations of smaller fish which remove ectoparasites from their skin. Because sunfish must consume a large volume of prey, their presence in a given area may be used as an indicator of nutrient-rich waters where endangered species may be found.

Feeding


The diet of the ocean sunfish consists primarily of various jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

. It also consumes salp
Salp
A salp or salpa is a barrel-shaped, planktonic tunicate. It moves by contracting, thus pumping water through its gelatinous body...

s, squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...

, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, small fishes, fish larvae, and eel grass
Zostera
Zostera is a small genus of widely distributed seagrass, commonly called marine eelgrass or simply eelgrass . The genus Zostera contains sixteen species.-Ecology:Zostera is found on sandy substrates or in estuaries submerged or partially floating...

. This range of food items indicates that the sunfish feeds at many levels, from the surface to deep water, and occasionally down to the seafloor in some areas. The diet is nutritionally poor, forcing the sunfish to consume a large amount of food to maintain its size.

The sunfish can pull in and spit out water through its small mouth to tear apart soft-bodied prey. Its teeth are fused into a beak-like structure, allowing it to break up harder organisms, and pharyngeal teeth
Pharyngeal teeth
Pharyngeal teeth are teeth in the pharyngeal arch of the throat of cyprinids, suckers, and a number of other fish species lacking teeth.Popular aquarium fish such as goldfish and loaches have these structures. Members of the Botia genus such as clown loaches are known to make distinctive clicking...

 located in the throat grind food into smaller pieces before passing them to the stomach.

Life cycle


Ocean sunfish may live up to ten years in captivity, but their lifespan in a natural habitat has not yet been determined. Their growth rate is also indeterminate. However, it is known that a young specimen at the Monterey Bay Aquarium
Monterey Bay Aquarium
The Monterey Bay Aquarium is located on the former site of a sardine cannery on Cannery Row of the Pacific Ocean shoreline in Monterey, California. It has an annual attendance of 1.8 million visitors. It holds thousands of plants and animals, representing 623 separate named species on display...

 increased in weight from 26 to 399 kg (57.3 to 879.6 lb) and reached a height of nearly 1.8 m (5.9 ft) in fifteen months.

The sheer size and thick skin of an adult of the species deters many smaller predators, but younger individuals are vulnerable to predation by bluefin tuna and mahi mahi. Adults are consumed by sea lion
Sea Lion
Sea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...

s, orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...

s and shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s. Sea lions appear to hunt sunfish for sport, tearing the fins off, tossing the body around, and then simply abandoning the still-living but helpless fish to die on the seafloor.

The mating practices of the ocean sunfish are poorly understood, but spawning areas have been suggested in the North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Oceans. Females can produce as many as 300 million eggs at a time, more than any other known vertebrate. Sunfish eggs are released into the water and externally fertilized
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...

 by sperm.

Newly hatched sunfish larvae are only 2.5 mm (0.0984251968503937 in) long. They grow to become fry, and those which survive grow many millions of times their original size before reaching adult proportions. Sunfish fry, with large pectoral fins, a tail fin and body spines uncharacteristic of adult sunfish, resemble miniature pufferfish
Pufferfish
Tetraodontidae is a family of primarily marine and estuarine fish of the Tetraodontiformes order. The family includes many familiar species which are variously called pufferfish, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, toadies, honey toads, sugar toads, and sea squab...

, their close relatives.
Young sunfish school for protection, but this behaviour is abandoned as they grow.

Human interaction


Despite their size, ocean sunfish are docile, and pose no threat to human divers. Injuries from sunfish are rare, although there is a slight danger from large sunfish leaping out of the water onto boats; in one instance a boy was knocked off his boat when a sunfish leaped onto it. Areas where they are commonly found are popular destinations for sport dives, and sunfish at some locations have reportedly become familiar with divers. In fact, the fish is more threatening to boaters than swimmers, as its immense size and weight can cause significant damage when struck by watercraft. Collisions with sunfish are very common in some parts of the world and may cause damage to the hull of a boat,
and their bodies can become lodged in the propellers of larger ships.

The meat of the ocean sunfish is considered a delicacy in some regions, the largest markets being Taiwan and Japan. All parts of the sunfish are used in cuisine
Fish (food)
Fish is a food consumed by many species, including humans. The word "fish" refers to both the animal and to the food prepared from it. Fish has been an important source of protein for humans throughout recorded history.-Terminology:...

, from the fins to the internal organs.
Some parts of the fish are used in some areas of traditional medicine. If the body does contain toxins, then the marketing and sale of ocean sunfish meat is forbidden in the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 according to Regulation (EC) No 853/2004 of the European Parliament and of the Council.

Sunfish are accidentally but frequently caught in drift gillnet
Gillnet
Gillnetting is a common fishing method used by commercial and artisanal fishermen of all the oceans and in some freshwater and estuary areas. The gillnet also is used by fisheries scientists to monitor fish populations. Because gillnets can be so effective their use is closely monitored and...

 fisheries, making up nearly 30% of the total catch of the swordfish fishery employing drift gillnet in California. The by-catch
By-catch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...

 rate is even higher for the Mediterranean swordfish industry, with 71% to 90% of the total catch being sunfish.

The fishery by-catch and destruction of ocean sunfish are unregulated worldwide. In some areas, the fish are "finned" by fishermen who regard them as worthless bait thieves; this process, in which the fins are cut off, results in the eventual death of the fish, because it can no longer propel itself without its dorsal and anal fins.
The species is also threatened by floating litter such as plastic bags which resemble jellyfish, its main food. Bags can choke and suffocate an individual or fill its stomach to the extent that it starves.

Many areas of sunfish biology remain poorly understood, and various research efforts are underway, including aerial surveys of mola populations,
satellite surveillance using pop-off satellite tags,
genetic analysis of tissue samples, and collection of amateur sighting data.
Recent studies indicate a decrease in sunfish populations that may be caused by more frequent bycatch and the increasing popularity of sunfish in human diet.

Sunfish in captivity


Sunfish are not widely held in aquarium exhibits, due to the unique and demanding requirements of their care. Some Asian aquariums display them, particularly in Japan. The Kaiyukan Aquarium
Osaka Aquarium Kaiyukan
The is an aquarium located in the ward of Minato in Osaka, Japan, near Osaka Bay. It is one of the largest public aquariums in the world, and is a member of the Japanese Association of Zoos and Aquariums ....

 in Osaka
Osaka
is a city in the Kansai region of Japan's main island of Honshu, a designated city under the Local Autonomy Law, the capital city of Osaka Prefecture and also the biggest part of Keihanshin area, which is represented by three major cities of Japan, Kyoto, Osaka and Kobe...

, Japan, is one of few aquariums with mola on display, where it is reportedly as popular an attraction as the larger whale shark
Whale shark
The whale shark, Rhincodon typus, is a slow-moving filter feeding shark, the largest extant fish species. The largest confirmed individual had a length of and a weight of more than , but unconfirmed claims report considerably larger whale sharks...

s.
The Lisbon Oceanarium
Lisbon Oceanarium
The Oceanarium is an oceanarium in Lisbon, Portugal. It is located in the Parque das Nações, which was the exhibition grounds for the Expo '98.- Architecture :...

 in Portugal is another aquarium where sunfish are showcased in the main tank, and in Spain, both the Valencia Oceanogràfic
L'Oceanogràfic
The Oceanographic is a marine park situated in the east of the city of Valencia, Spain, where different marine habitats are represented. It was designed by the architect Felix Candela and the structural engineers Alberto Domingo and Carlos Lazaro...

 and the Aquarium Barcelona
Aquarium Barcelona
-External links:...

 have specimens of sunfish.

The first ocean sunfish to be held in an aquarium in the United States arrived at the Monterey Bay Aquarium
Monterey Bay Aquarium
The Monterey Bay Aquarium is located on the former site of a sardine cannery on Cannery Row of the Pacific Ocean shoreline in Monterey, California. It has an annual attendance of 1.8 million visitors. It holds thousands of plants and animals, representing 623 separate named species on display...

in August 1986,
and this remains the only location in the country where the sunfish is displayed.
Because sunfish had not been kept in captivity on a large scale before, the staff at Monterey Bay were forced to innovate and create their own methods for capture, feeding, and parasite control. By 1998, these issues were overcome, and the aquarium was able to hold a specimen for more than a year, later releasing it after its weight increased by more than fourteen times. Mola mola have since become a permanent feature of the Outer Bay exhibit. Monterey Bay Aquarium's largest sunfish specimen was euthanized on February 14, 2008 after an extended period of poor health.

As the ocean sunfish is not highly maneuverable, preventing specimens from injuring themselves by rubbing against the walls of a tank is of major concern to curators. In a smaller tank, hanging a vinyl curtain has been used as a stopgap measure to convert a cuboid tank to a rounded shape and prevent the fish from scraping against the sides. A more effective solution is simply to provide enough room for the sunfish to swim in wide circles. The tank must also be sufficiently deep to accommodate the vertical height of the sunfish, which can be nearly as tall as it is long, and may reach a height of 3.2 m (10.5 ft).

Feeding captive sunfish in a tank with other faster-moving, more aggressive fish can also present a challenge. Eventually, the fish can be taught to respond to a floating target to be fed, and to take food from the end of a pole or from human hands.

Research and info


Images and videos