Mola mola

Sunfish have a bizarre appearance. The best way to describe them is with the term 'swimming head'. Every once in awhile, a sunfish is caught in the North Sea, or one is washed ashore. It is usually a small, young specimen weighing around 50 kilograms. Sunfish have a relatively long life expectancy and keep growing their entire life. There have been reports of sunfish 4 meters long and 2300 kilograms. Sunfish have two world records. They are the heaviest known bony fish and they lay the most eggs. They are even mentioned in the Guinness Book of World Records.

  Common names: sunfish (English), mola (Espanol), pez-sol (Espanol)
 
Mola mola (Linnaeus, 1758)

Ocean sunfish

Body a deep oval (depth usually ~ length), strongly compressed; mouth a horizontal slit when closed, opens at the front, is a beak (without a central suture) composed of teeth fused to the jaws; gill openings small, on side just before pectorals; pectorals short, rounded; no pelvics; dorsal 17-18 rays; anal 14-18 rays; pectoral 12-13 rays; no tail base;  dorsal and anal fins long and high, symmetrical, used for locomotion, at rear of body, their rear rays joined to tail fin immediately behind them that is reduced to a vertically elongate, short, blunt rudder, with bony ossicles on its margin, with an undulating rounded profile; skin thick, tough, with small denticles.

Grey brown to dark blue above, often with large pale blotches, silvery below, fins dark.

Size: 332 cm.

Habitat: oceanic.

Depth near surface, 0-644 m.

        Circumglobal, tropical to warm temperate; off Baja and the Gulf of California, and the Galapagos; potentially throughout our region.
   

Molas are distinguished for their distinct morphological characters which include reduced/fused caudal elements, presence of a clavus in place of the caudal fin, absence of a swim bladder and a degenerate, cartilaginous skeleton (Ref. 86435). Adults are found on slopes adjacent to deep water where they come in for shelter and for seeking cleaner fishes. They are usually shy. However, they may become familiar with divers in some locations (Ref. 48637). Individuals often drift at the surface while lying on its side but can swim actively and are capable of directional movements otherwise (Ref. 86435). They swim upright and close to the surface. The dorsal fin often protrudes above the water. Females are larger than males (Ref. 86435). This species has been filmed in 480 m depth with the help of a camera equipped with baits (Lis Maclaren, pers. comm. 2005). Adults eat fishes, mollusks, zooplankton, jellyfish, crustaceans and brittle stars (Ref. 4925, 5951, 48637). A live colony of the cirripede Lepas anatifera were found attached to the anterior portion of the sunfish's esophagus that was stranded in the south coast of Terceira Island, Azores Archipelago in 2004. This association has apparent advantages for the goose barnacles such as a regular intake of food and protection both from hydrodynamic hazards and from predators: but for the sunfish, it is not clear whether it is neutral, of advantage or causes feeding problems since the attachment may obstruct the sunfish's esophagus (Ref. 55063). The sunfish is registered as the heaviest bony fish and as the one with the most eggs in the Guinness Book of World Records (Ref. 6472). Generally this species is not used as food fish; some people consider it as a delicacy (Ref. 30573). The fish can be utilized fresh and can be broiled (Ref. 9988). Some parts of the fish are used in Chinese medicine (Ref. 12166). Molas may contain the same toxin as puffers and porcupine fish (Ref. 13513). They do not adapt well in captivity (Ref. 12382, 37040). Juveniles are victims of California sea lions in Monterey Bay (Ref. 37040).

 Silvery to brownish grey in colour. Body short and tall, flattened like a disc. Ventral fins absent. Caudal fin replaced by a stiff fringe of skin. Dorsal and anal fins modified to form long 'paddles' that can only move from side to side. Skin leathery without scales. Small eyes and mouth. May grow up to 4 m in length and 2 tonnes in weight.Often seen drifting at the surface while on its side or close to the surface with its dorsal fin projecting out of the water. Feeds on zooplankton, jellyfish, eel larvae and small deep sea fish.

Sunfish belong to the same group of fish as the pufferfish (Molidae). Members of this group have small mouths with beak-like teeth. The body is short and tall and flattened from side to side. The most striking characteristic of this species is the apparent absence of a tail as this is reduced to a stiff, frill-like membrane. In most fish the tail fin is the main means of propulsion, however in the sunfish the dorsal and anal fins are modified to form long 'paddles' which move from side to side. The upper half and fins are dark blue or grey-brown and the underside is silvery-white. This is one of the largest open water fish growing to a maximum length of approximately 3m. This species resembles the slender sunfish (Ranzania laevis) however this species is very rare in the seas around Britain and Ireland.

Depth Range (m): 0 (S) - 644 (S)

See Map (including site records) of Distribution in the Tropical Eastern Pacific 
 
Global Endemism: All species, TEP non-endemic, Circumtropical ( Indian + Pacific + Atlantic Oceans), "Transpacific" (East + Central &/or West Pacific), East Pacific + Atlantic (East +/or West), Transisthmian (East Pacific + Atlantic of Central America), East Pacific + all Atlantic (East+West)

Regional Endemism: All species, Eastern Pacific non-endemic, Tropical Eastern Pacific (TEP) non-endemic, Continent + Island (s), Continent, Island (s)

Residency: Resident

Climate Zone: North Temperate (Californian Province &/or Northern Gulf of California), Northern Subtropical (Cortez Province + Sinaloan Gap), Northern Tropical (Mexican Province to Nicaragua + Revillagigedos), Equatorial (Costa Rica to Ecuador + Galapagos, Clipperton, Cocos, Malpelo)

Newfoundland to Argentina

Ocean sunfish, Mola mola, are found in the temperate and tropical regions of the Mediterranean, Atlantic, Indian, and Pacific Oceans (Wheeler, 1969; Sims and Southall, 2002; Houghton et al., 2006). They are commonly observed off the coast of Southern California, Indonesia, the British Isles, the Northern and Southern Isles of New Zealand, the southern coasts of Africa, and in the Mediterranean and occasionally in the North Sea (Muus, 1964; Ayling and Cox, 1982; Smith, 1965; Cartamil and Lowe, 2004; Houghton et al., 2006; Sims and Southall, 2002; Konow et al., 2006). Most sightings in the British Isles and North Sea occur during the summer months, particularly June and July, when the waters are between 13 and 17˚C (Sims and Southall, 2002). Ocean sunfish are thought to migrate to higher latitudes during the spring and summer months to pursue their migrating zooplankton prey (Liu et al., 2009).

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Warm and temperate zones of all oceans. Eastern Pacific: British Columbia, Canada (Ref. 2850) to Peru and Chile (Ref. 5530). Western Pacific: Japan to Australia (Ref. 86345). Eastern Atlantic: Scandinavia to South Africa (occasionally western Baltic, Mediterranean). Western Atlantic: Newfoundland, Canada (Ref. 7251) to Argentina (Ref. 36453).

Circumglobal in tropical through temperate seas (including western Baltic Sea, North Sea, Mediterranean Sea, Mascarenes, Red Sea, Hawaiian Islands).

Tropical and temperate seas; northward to northern Norway in the eastern Atlantic, to the Newfoundland banks, the Gulf of St. Lawrence, and the coast of Nova Scotia in the western Atlantic.

The sunfish is distributed throughout the world in warm and temperate seas. In the British Isles they are mostly encountered late in the summer around August and September.

Length max (cm): 332.0 (S)

Ocean sunfish have a large body that is compressed and ovular. They are the largest bony fish, measuring up to 3.1 m in length, 4.26 m in height, and weighing up to 2235 kg (Hutchins, 2004; Humann and Deloach, 2002; Houghton et al., 2006). They are scale-less, and have a thick, rubbery skin and irregular patches of tubercles over their body (Hutchins, 2004; Wheeler, 1969; Smith, 1965). Notably, adult ocean sunfish do not have a caudal fin or caudal peduncle. They instead have a clavus, which is a truncated tail, used more like a rudder than for propulsion. The clavus reaches from the rear edge of the dorsal fin to the rear edge of the anal fin (Wheeler, 1969; Hutchins, 2004; Linnaeus, 1758). The dorsal and anal fins of ocean sunfish are tall, and their small pectoral fins point toward the dorsal fin (Hutchins, 2004). The dorsal fin has 15 to 18 soft rays, and the anal fin has 14 to 17 soft rays (Hutchins, 2004). They also have a small mouth with fused teeth that form a beak-like structure (Hutchins, 2004).

Ocean sunfish vary in coloration, though the head, back, tips of the anal and dorsal fins, and clavus are generally a mixture of dark grey-brown and dark silvery grey (Hutchins, 2004; Humann and Deloach, 2002; Ayling and Collins, 1982). They have a white belly and sometimes have white splotches on their fins and dorsal side (Ayling and Collins, 1982; Humann and Deloach, 2002). Adult ocean fish do not possess a lateral line, and only one gill opening is visible on each side, which is located near the base of the pectoral fins (Hutchins, 2004; Smith and Heemstra, 1986).

Range mass: 2235 (high) kg.

Range length: 3.1 (high) m.

Other Physical Features: ectothermic ; bilateral symmetry

Dorsal spines (total): 0; Dorsal soft rays (total): 15 - 18; Analspines: 0; Analsoft rays: 14 - 17

Maximum size: 3330 mm TL

333 cm TL (male/unsexed; (Ref. 26340)); max. published weight: 2,300.0 kg (Ref. 47360)

to 332 cm TL (male/unsexed); max. weight: 2,000 kg.

It often drifts at the surface while lying on its side, or swims upright and so close to the surface that the dorsal fin projects above the water. Sometimes reaches depths of up to 300 m (Ref. 9317). Feeds on animal plankton, eel larvae, small deep-sea fishes; also on jellyfish, crustaceans, molluscs, and brittlestars (Ref. 4925). In Guiness Book of Records it was recorded as the heaviest bony fish and as the one with the most eggs (Ref. 6472). Also occasionally caught with encircling nets (Ref. 9119) and harpoon (Ref. 9988). Mola is the latin word for millstone. Utilized fresh and can be broiled (Ref. 9988).

The scaleless body is covered with extremely thick, elastic skin. The caudal fin is replaced by a rudder-like structure called 'clavus'. Dorsal and anal fins very high with short base; in swimming, these fins are flapped synchronously from side to side and can propel the fish at surprisingly good speed. Pectorals small and rounded, directed upward (Ref. 6885). Mouth very small; teeth fused to form a parrot-like beak. Gills 4, a slit behind the last; gill openings reduced to a small hole at the base of the pectoral fins. Gas bladder absent in adults.Description: Characterized further by deep and oval body, nearly circular, depth 1-1.5 in TL; rough texture of skin; clavus supported by about 12 fin rays, of which 8-9 bear ossicles (Ref. 90102).

Salinity: Marine, Marine Only

Inshore/Offshore: Offshore Only, Offshore

Water Column Position: Surface, Near Surface, Mid Water, Water column only

Habitat: Water column

FishBase Habitat: Pelagic

Known from seamounts and knolls

nektonic

Found in warm and temperate seas, often drifting on the surface.

Adult ocean sunfish are found in temperate and tropical oceans across the globe. They prefer the open ocean but occasionally venture into kelp beds and deep coral reefs in order to be cleaned of parasites by fishes such as wrasses (Labroides dimidiatus and Thalasoma lunare) and Emperor Angelfish (Hutchins, 2004; Humann and Deloach, 2002, Konow et al., 2006).

Habitat Regions: saltwater or marine

Aquatic Biomes: pelagic

pelagic-oceanic; oceanodromous (Ref. 51243); marine; depth range 30 - 480 m, usually 30 - 70 m (Ref. 90102)

Habitat Type: Marine

Depth range based on 3553 specimens in 1 taxon.
Water temperature and chemistry ranges based on 2881 samples.

Environmental ranges
  Depth range (m): 0 - 2450
  Temperature range (°C): 3.126 - 26.831
  Nitrate (umol/L): 0.119 - 26.285
  Salinity (PPS): 30.381 - 36.508
  Oxygen (ml/l): 4.081 - 7.599
  Phosphate (umol/l): 0.045 - 1.609
  Silicate (umol/l): 0.565 - 25.103

Graphical representation

Depth range (m): 0 - 2450

Temperature range (°C): 3.126 - 26.831

Nitrate (umol/L): 0.119 - 26.285

Salinity (PPS): 30.381 - 36.508

Oxygen (ml/l): 4.081 - 7.599

Phosphate (umol/l): 0.045 - 1.609

Silicate (umol/l): 0.565 - 25.103
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

 Distributed throughout the world in tropical and temperate seas in open water to a depth of at least 360 m.

Depth: 0 - 300m.
Recorded at 300 meters.

Habitat: pelagic.

Pelagic; marine; depth to 300 m. Seen drifting at the surface lying on its side, or swimming upright near the surface so its dorsal fin projects above the water.

Sunfish live in open water and are usually spotted swimming or drifting at the surface of the water. They mostly feed on planktonic animals, especially jelly-fish, salps and comb-jellies.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Oceanodromous. Migrating within oceans typically between spawning and different feeding areas, as tunas do. Migrations should be cyclical and predictable and cover more than 100 km.

Feeding Group: Planktivore

Diet: octopus/squid/cuttlefish, Pelagic crustacea, pelagic jellyfish/ctenophores, zooplankton, pelagic fish larvae, bony fishes

Ocean sunfish primarily feed on jellyfish and gelatinous zooplankton, such as ctenophores, salps, and medusae. They have also been known to eat soft bodied invertebrates, crustaceans, mollusks, seaweed, eel larvae, and even flounder (Wheeler, 1969). Ocean sunfish are thought to migrate to higher latitudes in response to zooplankton migrations during the spring and summer months (Liu et al., 2009). They may also migrate vertically during the day to prey upon jellyfish and zooplankton found below the thermocline (Cartamil and Lowe, 2004; Liu et al., 2009).

Animal Foods: fish; mollusks; aquatic crustaceans; cnidarians; zooplankton

Plant Foods: macroalgae

Primary Diet: herbivore (Algivore); planktivore

The fish is found on slopes adjacent to deep water. The fish comes in for shelter and for seeking cleaner fishes. The fish is usually shy. However, it may become familiar with divers in some locations (Ref. 48637). The species often drifts at the surface while lying on its side. It swims upright and close to the surface. The dorsal fin often protruds above the water. The species has been filmed in 480 m depth with the help of a camera equipped with baits(Lis Maclaren, pers. Comm. 2005). The species eats fishes, mollusks, zooplankton, jellyfish, crustaceans and brittle stars (Ref. 4925, 48637). A live colony of the cirriped Lepas anatifera were found attached to the anterior portion of the sunfish's esophagus that was stranded in the south coast of Terceira Island, Azores Archipelago in 2004; an association with apparent advantages for the goose barnacles such as a regular intake of food and protection both from hydrodynamic hazards and from predators: but for the sunfish, it is not clear whether it is neutral, of advantage or causes feeding problems since the attachment may obstruct the sunfish's esophagus (Ref. 55063). Parasites of the species include 1 monogenean, 6 trematodes, 3 cestodes and 4 copepods (Ref. 5951). The fish is registered as the heaviest bony fish and as the one with the most eggs in the Guinness Book of World Records (Ref. 6472).

Fishes, mollusks, zooplankton, jellyfish, crustaceans, and brittle stars.

Ocean sunfish are considered to have strategic top-down control of jellyfish populations. They may also have a direct influence on the incidence and occurrence of jellyfish blooms (Liu et al., 2009).

Ecosystem Impact: keystone species

Ocean sunfish are often preyed upon by large sharks and California sea lions (Cartamil and Lowe, 2004). They may dive below the thermocline to avoid predators (Cartamil and Lowe, 2004). Ocean sunfish are also occassionally hunted by humans.

Known Predators:

• large sharks Selachimorpha
• California sea lions Zalophus californianus
• humans Homo sapiens

Mola mola (ocean sunfish) is prey of:
Chondrichthyes

Based on studies in:
unknown (epipelagic zone, Tropical)

This list may not be complete but is based on published studies.

Mola mola (ocean sunfish) preys on:
Copepoda

Based on studies in:
unknown (epipelagic zone, Tropical)

This list may not be complete but is based on published studies.

Sims et al. (2009) used a fast-acquisition global positioning system (Fastloc GPS) tag with remote data retrieval to track long-term movements of three Ocean Sunfish (Mola mola) captured and tagged off southern Portugal. This allowed tracking in near real time with position accuracy of <70 m. These fish are known to dive to depths of at least 472 m and can often remain at deep depths for long periods, only returning occasionally, and then often only briefly, to the surface. The system implemented permitted reception and transmission of location information whenever the fish came close to the surface.

According to Sims et al., their study represents the first demonstration of long-term (>90 days) GPS tracking of a large pelagic fish and shows the great potential for this technique, whereby GPS-quality location data are retrieved remotely via conventional Argos satellites. By freeing researchers from the restriction of working on estuarine or nearshore species in order to physically recover tags to download GPS acquisition data, this technique offers tremendous potential for tracking large pelagic fish species that surface relatively frequently. Although the high spatial accuracy of this technique for fish in open ocean habitats has practical applications for both fisheries and conservation, it will not be suitable for fish species that remain in deep water after tagging.

In the early part of the 20^th Century, Ocean Sunfish were sometimes described as active swimmers, but in other cases described as sluggish, inefficient swimmers, passively carried by ocean currents. Modern tracking studies of these fish using attached acoustic transmitters, acceleration dataloggers, and satellite-linked archival transmitters have demonstrated that they are active swimmers both horizontally and vertically. Sims et al. (2009) found that the Ocean Sunfish they tracked covered around 10 to 20 km per day, a rate that is comparable to the movements of pelagic sharks. GPS track integration with current direction/strength maps showed individuals often headed into and across prevailing currents associated with mesoscale eddies. These data confirm that Ocean Sunfish are not passive drifters, but rather, are in fact active swimmers with movement rates within the range observed for other pelagic fishes. Search-like movements occurred over at least three distinct spatial scales. At fine scales, Ocean Sunfish spent longer in highly localised areas with faster, straighter excursions between them. These "stopovers" during long-distance movement appear consistent with finding and exploiting food patches.

Sims et al. (2009) suggest that there would be great value in pursuing long-term GPS tracking of other large pelagic fish species--such as tunas, billfish, and sharks--that surface relatively frequently and have high conservation priority in many ocean regions where a greater understanding of when and why they use certain habitats could enhance management.

Feeds on fishes, mollusks, zooplankton, jellyfish, crustaceans and brittle stars

Little is known regarding methods of communication and perception of ocean sunfish.

Perception Channels: tactile ; chemical

Ocean sunfish have two larval stages. Larvae in the first tetradon-like stage are round and spines protrude from the edges of their body. They have a well-developed tail and caudal fin (Bass et al., 2005; Muus, 1964) During the second larval stage, the tail is completely absorbed and spines disappear (Bass et al., 2005). Larvae generally measure about 0.25 cm in length (Pope et al., 2010). Juvenile ocean sunfish grow at an considerable rate, averaging 0.02 to 0.42 kg/day and sometimes reaching 0.82 kg/day (Pope et al., 2010).

Produces very numerous and small eggs; 300 million eggs found in a 1.5 m long female (Ref. 4711). Oocytes in the ovaries develop in different stages suggesting Mola mola as a multiple spawner (Ref. 86440). This is the largest clutch estimate for this species (Ref. 53596).

The lifespan of ocean sunfish is currently unknown. A member of the same family, sharptail mola are estimated to have a lifespan of 82 to 105 years (Liu et al., 2009).

Observations: Very little is known about the longevity of sunfishes, though given their their large body size and reproductive output it is possibly they are long-lived. They can lay 300,000,000 eggs. Anecdotes suggest they can live more than 10 years in captivity, but possibly much longer (http://www.oceansunfish.org/).

Egg Type: Pelagic, Pelagic larva

Little is known about the mating systems of ocean fish, although they are thought to have paired courtship (Muus,1964; Hutchins, 2004). Some individuals are thought to spawn in the Sargasso Sea.

Little is known about the breeding behaviors of ocean sunfish. Off the coast of Japan, spawning is thought to occur between August and October (Nakatsubo et al., 2007). Female ocean sunfish can produce over 300 million eggs each breeding season, making them the most fecund extant vertebrate (Bass et al., 2005). Their eggs are very small, with an average diameter of 0.13 cm (Pope et al., 2010).

Range number of offspring: 300,000,000 (high) .

Little is known regarding parental investment of offspring in ocean sunfish.

Numerous and small eggs (300 million in a female 1.5 m long). Three developmental stages : (1) tetraodontiform-body rather elongate, no spines, caudal fin present;(2) ostracioniform-body shortened, with some large spines on body plates;(3) molacanthiform (Molacanthus)-body short and high, skin rough with minute spines.

IUCN Red List: Not evaluated / Listed

CITES: Not listed

Ocean sunfish have not been evaluated by the IUCN, US Federal List, or CITES. They are often caught as bycatch by drift gillnet fisheries. In southern California, ocean sunfish compromised 29% of the catch in drift gillnet fisheries targeting swordfish (Cartamil and Lowe, 2004). In the Mediterranean between 1992 and 1994, ocean sunfish had a bycatch rate of 70 to 93%. In South Africa, the bycatch rate of ocean sunfish is estimated at 17% (Liu et al., 2009).

US Federal List: no special status

CITES: no special status

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: GNR - Not Yet Ranked

Not Evaluated

Ocean sunfish are often caught as bycatch in commercial fishing nets, which can be a great inconvenience (Liu et al., 2009).

Ocean sunfish are considered a delicacy in some Asian countries. They are also used in traditional Chinese medicines (Humann and Deloach, 2002).

Positive Impacts: food ; body parts are source of valuable material

fisheries: minor commercial; price category: unknown; price reliability: