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Ocean Sunfish
Mola mola (Linnaeus, 1758)
Ocean Sunfish viewed from above.
On 13th October 1998, staff of the Australian Museum were called to examine an Ocean Sunfish, Mola mola, that was found stuck on the bulbous bow of the cement carrier, MV Goliath, as it tied up to the wharf in Sydney.
The huge fish, which weighed approximately 1400 kg was removed from the bow of the ship by the Sydney Waterways Authority. The fish became stuck on the bow off Jervis Bay, New South Wales. It caused the speed of the ship to slow from 14 to 11 knots. The skin of the Ocean Sunfish was so rough it wore the ship's paint work back to the bare metal.
Mark and Shaun measuring the fish.
The fish measured 3.1 m from the tip of the dorsal fin to the tip of the anal fin, and 2.5 m from the tip of the snout to the end of the clavus. Skin samples were taken from above the pectoral fin and near the tail. These are registered in the Australian Museum Ichthyology Collection as AMS I.38997-001 and AMS I.38997-002.
This Sunfish is not the first to meet its end by being struck by a ship. On 18 September 1908, the Steamer Fiona, was 65 km from Sydney when it suffered a ‘violent concussion’. A boat was lowered over the side and the men onboard saw a Sunfish jammed in the framework of the port propeller. The fish was the largest known at the time, measuring ’10 feet, 2 inches’ (3.1 m) in length and ’13 feet, 4 inches’ (4.1 m) in height.
The Ocean Sunfish occurs in temperate marine waters worldwide. In Australia, it has been recorded from the central coast of New South Wales to Tasmania and west to Mandurah, Western Australia. Ocean Sunfish are usually found in oceanic waters, but occasionally come inshore. Sunfishes are often seen at the surface where they may be mistaken for sharks, because of the large dorsal fin.
The clavus of the Ocean Sunfish. Note the distinct line where the course body denticles change to fine denticles on the clavus.
The Ocean Sunfish is an unusual looking fish. It doesn't have a caudal fin. Instead it has a clavus, which is formed by extensions of the dorsal and anal fin rays. These take the place of a true tail fin which does not form. The clavus is broadly rounded and has low, rounded projections (called ossicles) which make up the margin. Characters that help separate this species from the other four members of the family are the number of ossicles and the presence of a definite line at the posterior end of the body where the denticles on the skin change from extremely coarse to very fine.
The fused parrot-like teeth of the Ocean Sunfish.
Sunfishes are harmless to people. They feed on jellyfish, salps, ctenophores and occassionally small crustaceans and fishes. The teeth in each jaw are fused to form a plate, and the mouth is small in comparison to the body size.
In some areas, the Ocean Sunfish is a commercial species that is caught for human consumption.
The Ocean Sunfish belongs to the family Molidae and is one of three species recorded from New South Wales waters. The other two are the Southern Ocean Sunfish, and the Slender Sunfish, Ranzania laevis (view larva). The fourth Australian species is the Sharptail Sunfish, Masturus lanceolatus. It occurs in southern waters of South Australia and Western Australia.
Related links
- Historic image of sunfish on rope and tackle.
- Larval Ocean Sunfish page
- Ocean Sunfish in the collection
- Ocean Sunfish stranding in 2002
- Sharptail Sunfish fact sheet
- View a low resolution movie clip (126k) of an Ocean Sunfish. Go to the movies page for high and low resolution versions.
Further Reading
- Anon. 2003. OceanSunfish.org. http://www.oceansunfish.org/index.html
- Glover, J.C.M. in Gomon, M.F, J.C.M. Glover & R.H. Kuiter (Eds). 1994. The Fishes of Australia's South Coast. State Print, Adelaide. Pp. 992.
- Matsuura, K. & J.C. Tyler. in Paxton, J.R. & W.N. Eschmeyer (Eds). 1994. Encyclopedia of Fishes. Sydney: New South Wales University Press; San Diego: Academic Press. Pp. 240.
- Paulin, C., Stewart, A., Roberts, C. & P. McMillan. 1989. New Zealand Fishes. A Complete Guide. National Museum of New Zealand. Pp. 279.
- Stead, D.G. 1933. Giants and Pigmies of the Deep. A story of Australian Denizens. Shakespear Head Australian Nature Books. Pp. 108.
