Common clownfish (Amphiprion ocellaris)
|Also known as:||clown fish, clownfish, common clown fish, false clown anemonefish, false percula clown fish, false percula clownfish, ocellaris clown fish, ocellaris clownfish, orange clown fish, orange clownfish|
|Size||Maximum length: 11 cm (2)|
The common clownfish has not yet been assessed by the IUCN.
Most famed for inspiring the character Nemo in the Walt Disney film ‘Finding Nemo’, the common clownfish (Amphiprion ocellaris) is the most familiar of the clownfish and the species most frequently found in pet shops (3) (4). Like other clownfish, this species is brightly coloured, the bright orange body contrasting with three bold, white, vertical stripes that have black edges. There is also a thin black line around the tips of each fin (3) (5).
The common clownfish is almost identical in appearance to the clown anemonefish (Amphiprion percula), but has 11 spines in the dorsal fin compared to 10, while the spiny part of the dorsal fin is also taller (3).
The common clownfish is found in the Indo-West Pacific, where it ranges from the eastern Indian Ocean, to Southeast Asia, including Indonesia and the Philippines, northwest Australia, and north to Taiwan (2).
The common clownfish is usually found on shallow water coral reefs, where it lives amongst the venomous tentacles of the carpet anemones Stichodactyla gigantea and Stichodactyla mertensi, as well as the anemone Heteractis magnifica. However, it may also be found around outer reefs and in shallow lagoons to depths of about 15 metres (6) (7).
Clownfish are the only fish known to be able to live amongst the tentacles of anemones (5). The tentacles of the anemones normally sting other fish, but clownfish excrete a mucus over their skin that tricks the anemone into believing it is touching itself, so it does not sting (4). Both the anemone and clownfish live in a symbiotic relationship, meaning the anemone benefits from the presence of the clownfish, while the clownfish benefits from living with the anemone (5). It is thought that the clownfish feeds upon parasites and debris amongst the anemone’s tentacles (3), and in return scares away fish that may prey upon the anemone, as well as giving the anemone better water circulation as it fans its fins while swimming around (5). It is possible that the clownfish also lures fish for the anemone to kill and eat (3).
Clownfish are highly territorial, living in groups that guard their host anemone against other clownfish (4). There is a strong hierarchy within these groups, with the largest female dominating (5). Only the largest male breeds with the dominant female (3). All clownfish are born with active male and dormant female reproductive organs, meaning they all start life as a male. If the dominant female dies, the largest male will change into a female and a non-dominant male will take his place as the new dominant male. This process, known as ‘protandrous hermaphrorditism’, allows the group of clownfish to remain self-sufficient, as when the dominant female dies the male does not need to search for a new mate (3).
Breeding in clownfish may occur all year round. Breeding begins with males attracting females through courtship behaviours that including chasing, biting and extending the fins (5). Spawning takes place on a cleaned piece of coral or rock next to an anemone (4), where the female releases between 100 and 1,000 eggs which are then fertilised by the male. The male clownfish guards and protects the eggs until they hatch four to five days later, but both the male and female care for the eggs by fanning their fins and by removing litter or dead eggs (5). Once hatched, the young clownfish spend about two weeks floating in the open sea, before settling on a coral reef and finding a host anemone (4). In captivity, clownfish have been known to live for up to 12 years (2).
The greatest threat to the common clownfish is global climate change, which threatens this species through a combination of habitat loss, disruption of its senses and direct effects on its behaviour (8).
The expected rise in ocean temperature associated with climate change threatens coral reefs by increasing the frequency of bleaching events, in which the stressed coral expels its symbiotic algae known as ‘zooxanthellae’, often resulting in the death of the coral. Climate change may also lead to more frequent severe storms, which can damage reefs. Rising carbon dioxide levels may also make the ocean increasingly acidic. Such stresses can make corals more susceptible to disease, parasites and predators (9) (10) (11). The common clownish may adapt to this loss of habitat by moving to new reefs, but its ability to do so is limited by the great rate at which its habitat is being degraded and by its general lack of mobility (8).
Increases in ocean acidity levels have also been shown to affect clownfishes’ ability to detect the chemical signals necessary for navigating to anemones. Clownfish that are unable to locate a hiding place are at a much higher risk of predation, and are much less likely to find other clownfish with which to mate. Furthermore, an extended period away from their host commonly leads to the loss of their immunity to the anemones’ poison, which also leads to a greater risk of predation. This effect is known to be particularly severe in juvenile clownfish (8).
A further threat to clownfish associated with climate change relates to their reproductive behaviour. Clownfish only reproduce within a very small temperature range. Therefore, an increase in temperature could discourage clownfish from breeding. High temperatures have also been shown to cause eggs to perish and to cause juvenile clownfish to develop faster. Individuals will therefore reproduce earlier, meaning they will disperse only a short distance from their parents’ anemone before their development triggers them to find their own anemone. This could result in greater competition for host anemones, greater chance of predation and increased inbreeding (8).
With an estimated 20 percent of the world’s coral reefs already destroyed, the common clownfish also faces many of the other threats that are affecting coral reef communitites globally. Worldwide, there is increasing pressure on coastal resources resulting from human population growth and development. There has been a significant increase in domestic and agricultural waste in the oceans, poor land-use practices that result in an increase in sediment running onto the reefs, and over-fishing, which can have ‘knock-on’ effects on the reef (9) (10) (11).
The common clownfish has not been the target of any known conservation measures. Further research is required to determine this species’ capacity to adapt to climate change, including its ability to use soft corals as alternative habitat (8).
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- Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
- Dorsal fin: the unpaired fin found on the back of the body of fish, or the raised structure on the back of most cetaceans.
- Fertilisation: the fusion of gametes (male and female reproductive cells) to produce an embryo, which grows into a new individual.
- Spawning: the production or depositing of large quantities of eggs in water.
- Symbiotic: describes a relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).
- Territorial: describes an animal, a pair of animals or a colony that occupies and defends an area.
Integrated Taxonomic Information System (ITIS) (February, 2011)
FishBase - Common clownfish (February, 2011)
MarineBio - Common clownfish (February, 2011)
Bristol Zoo - Clownfish (February, 2011)
Tree of Life - Clownfish (February, 2011)
- Tullock, J.H. (1998) Clownfish and Sea Anemones. Barron’s Educational Series, New York.
- Tullock, J.H. (2007) Saltwater Aquarium Models: Recipes for Creating Beautiful Aquariums That Thrive. Wiley Publishing, New Jersey.
IUCN (2009) Species and Climate Change: More than Just the Polar Bear. IUCN/Species Survival Commission, Cambridge, UK. Available at:
- Wilkinson, C. (2004) Status of Coral Reefs of the World: 2004. Volume 3. Australian Institute of Marine Science, Townsville, Australia.
- Carpenter, K.E. et al. (2008) One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science, 321: 560-563.
- Miththapala, S. (2008) Coral Reefs. Coastal Ecosystems Series (Volume 1). Ecosystems and Livelihoods Group Asia, IUCN, Colombo, Sri Lanka.