Napoleon fish, Cheilinus undulatus (Biology, distribution, threats and conservation) – Video

This short clip was taken at the Sea World, California, USA
Source:  –  Video and text ownership: Abdel Rahman ElGamal

Introduction: The Napoleon fish, Cheilinus undulatus has more common names including humphead wrasse, humphead or Maori wrasse. This species one of the largest members of the family Labridae as well as all coral reef fishes in the world. The species can live for more than 30 years. Despite their large size, they are friendly with divers who approach their habitats in coral reefs.

Description: Males of Napoleon fish reach up to 2 m in length, while females rarely exceed about 1 m. The species has thick, oversize fleshy lips and a hump that forms on its head above the eyes, becoming more prominent as the fish ages. Males range in color from a bright electric blue to green, a purplish blue color while females are red-orange in color.

Distribution and habitats: The species is widely distributed on coral reefs of the Indo-Pacific. Adults are commonly found on the outer reef slope habitats. The juveniles tend to prefer a more cryptic existence in areas of dense branching corals, bushy macroalgae or seagrasses. The species is most often observed in solitary male-female pairs, or small groups. In general, they tend to move into somewhat deeper waters as they grow older and larger.

Feeding habits: Napoleon fish are opportunistic predators preying primarily on crustaceans, mollusks – particularly gastropods- fish, echinoderms. The tough teeth enable fish to crush shells of their prey. Napoleon fish can predate on toxic species such as crown of thorns starfish, boxfishes and sea hares. The ability to prey on thorns star fish, Acanthaster planci represents a significant support to coral reef ecosystem that is often threatened by starfish. Heavy shells are crushed with the tough pharyngeal teeth. Napoleon fish are active during the day and rest during night. Their large size means that they have no natural predators apart from large sharks.

Reproduction and life history: Individuals of Napoleon fish reach their sexual maturity in about 5 to 7 years. The species are protogynous hermaphrodites which mean that the individuals first are reproductively active as females and as they age to approximately 9 years old, adult females are known to change to adult males.
Ready to mate fish migrate to the spawning areas whereas males are known to arrive first, to be joined later by females. Spawning which has been observed in several months is believed to be associated with certain tidal cycles but not with specific lunar phases. The sex ratio has been found to be about 10-15 females per male. The planktonic eggs are released into the water column and drift away from the spawning site. After hatching, the larvae stay in the water until they settle on the substrate. As the larvae grow, they move from shallow inshore waters to deeper offshore reef.

Threats: The high value of wild-caught live Napoleon fish in export trade, aquarium trade or for fattening in cages stand behind most of the threats facing this species which is considered a delicacy in parts of Asia, especially Hong Kong, Singapore and Taiwan. The high demands on this luxury fish led to overfishing and to applying hazardous fishing practices such as the use of sodium cyanide, dynamite or spears. The major of the international trade is in live fish although a small part is traded in a chilled form. The Mainland China and Hong Kong are major importers to Napoleon fish while exports are done by and through Malaysia, Singapore and the Philippines. The listing of Napoleon fish under CITES Appendix II as well as endangered on the IUCN Red List reflect the status of this rare species.

Conservation measures: The biological characteristics of this species especially the longevity and slow breeding rate, indicates to the long time required before feeling the recovery of the species assuming that conservation measures are in place. Various measures have been adopted. The control measures have addressed the fishing and trading of the species. For example, fishing and exporting fish below 1 kg and above 3 kg has been banned in Indonesia. Moreover, total banning of fish catch was enforced in Australia. Specifying allowable catch size or the necessity to get fishing and/or export permit are examples of conservation measures. Emphasis has been placed on banning the use of cyanide in fishing while limiting the fishing method to the traditional fishing. Exceptions have been given to education, research and aquarium displays. The public campaigns reached the restaurants expressing the opposition to serving this endangered fish.

The Society for the Conservation of Reef Fish Aggregations,
The changing ocean
Yvonne Sadovy and Santi Suharti. Napoleon fish, Cheilinus undulatus, Indonesia

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