|Breeding male humphead wrasse in the Melbourne Aquarium|
The humphead wrasse (Cheilinus undulatus) is a large species of wrasse mainly found on coral reefs in the Indo-Pacific region. It is also known as the Māori wrasse, Napoleon wrasse, Napoleon fish, Napoleonfish, so mei 蘇眉 (Cantonese), mameng (Filipino), and merer in the Pohnpeian language of the Caroline Islands.
The humphead wrasse is the largest living member of the family Labridae. Males, typically larger than females, are capable of reaching up to 2 meters and weighing up to 180 kg, but the average length is a little less than 1 meter. Females rarely grow larger than one meter. This species can be easily identified by its large size, thick lips, two black lines behind its eyes, and the hump on the foreheads of larger adults. Its color can vary between dull blue-green to more vibrant shades of green and purplish-blue. Adults are usually observed living singly, but are also seen in male/female pairs and in small groups.
The humphead wrasses can be found on the east coast of Africa around the mouth of the Red Sea, and in some areas of the Indian and Pacific Oceans. Juveniles are usually found in shallow, sandy ranges bordering coral reef waters, while adults are found mostly in offshore and deeper areas of coral reefs, typically in outer-reef slopes and channels, but also in lagoons. 
The humphead wrasse is long-lived, but has a very slow breeding rate. Individuals become sexually mature at five to seven years, and are known to live for around 30 years.  They are protogynous hermaphrodites, with some becoming male at about 9 years old. The factors controlling the timing of sex change are not yet known. At certain times of year, adults move to the down-current end of the reef and form local spawning aggregations (groups). They likely do not travel very far for their spawning aggregations.
The pelagic eggs and larvae ultimately settle on or near coral reef habitats. Eggs are 0.65 mm in diameter and spherical, with no pigment.
Very opportunistic predators, C. undulatus preys primarily on invertebrates such as mollusks (particularly gastropods, as well as pelecypods, echinoids, crustaceans, and annelids) and fish. Because half of echinoids and most pelecypods hide under the sand, wrasses may rely on fish excavators like stingrays, or they themselves may excavate by ejecting water to displace sand and nosing around for prey. Like many other Red Sea wrasses, humphead wrasses often crack sea urchins (echinoids) by carrying them to a rock in their mouths and striking them against the rock with brisk, sideways head movements.
Adults are commonly found on steep coral reef slopes, channel slopes, and lagoon reefs in water 3 to 330 ft (0.91 to 100.58 m) deep. The species actively selects branching hard and soft corals and seagrasses at settlement. Juveniles tend to prefer a more cryptic existence in areas of dense branching corals, bushy macroalgae or seagrasses, while larger individuals and adults prefer limited home ranges in more open habitat on the edges of reefs, channels and reef passes.
- Intensive, species-specific removal by the live reef food-fish trade throughout its core range in Southeast Asia
- Destructive fishing techniques, including bombs and cyanide
- Habitat loss and degradation
- Local consumption, and its perception as a delicacy to locals and tourists
- A developing export market for juveniles for the marine aquarium trade
- Lack of coordinated, consistent national and regional management
- Inadequate knowledge of the species
- Illegal, unregulated and unreported fishing
Unsustainable and severe overfishing within the live reef food fish trade (LRFFT) is the primary threat. Sabah, on Borneo Island, is a major source for humphead wrasses. The fishing industry is vital to this state because of its severe poverty. The export of humphead wrasses out of Sabah has led to a roughly 99% decline in the area's population. In an effort to protect it, export of the humphead wrasse out of Sabah has been banned; however, it has not prevented illegal, unreported and unregulated activities (IUU). Protection by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) is managed in this area by the federal Department of Fisheries Malaysia, Sabah (DOFS) who issue permits to regulate fishing activity. Two pieces of legislation have also been implemented to protect the species: The Fisheries Act 1985 controls the transport of live fish and prohibits destructive fishing techniques; and the Trade of Endangered Species Act 2008 supports Malaysia's adoption of CITES.
The humphead wrasse is considered an umbrella species, which means many other species are sympatric with it and have much smaller ranges—thus the conservation of the humphead wrasse's habitat would benefit these other species as well. Understading the concept of an umbrella species can lead to a better understanding of endangered species protection.
The humphead wrasse has historically been fished commercially in northern Australia, but has been protected in Queensland since 2003 and in Western Australia since 1998.
In Guangdong Province, southern mainland China, permits are required for the sale of the species. Indonesia allows fishing only for research, mariculture and licensed artisanal fishing. The Maldives instituted an export ban in 1995; Papua New Guinea prohibits export of fish over 2 ft (61 cm); and Niue has banned all fishing for this species.
The U.S. National Marine Fisheries Service has classified the humphead wrasse as a species of concern—one about which it has concerns, but for which it lacks insufficient information to list it under the Endangered Species Act.
Population conservation by genetics
In 1996, following a decade of rapid population decline, the humphead wrasse was placed on the IUCN Red List of endangered species. The wrasse's genomes must be analyzed to help keep the species alive.
Since so little was known about the wrasse's genetic relationships at a geographical scale, researchers utilized a test using microsatellite loci to facilitate population genetic studies. (DNA markers could not be used for testing, as the humphead wrasse lack such markers.) Of the 15 microsatellite loci used in the test, only four seemed to have different outcomes than the other 11. These loci were all prone to null alleles. However, with the presence of these null alleles, the results may have been slightly biased, or they may be related to a particularity of the C. undulatus, which are highly restricted to coral reef habitats.
Illegal, unregulated and unreported activities (IUU)
The Philippines, Indonesia and Sabah Malaysia are the three largest exporters of the humphead wrasse. It has one of the highest retail values in Asia, especially when caught alive, and it is considered a delicacy in places like Malaysia. IUU activities have been identified as the major factor for the failure of conservation efforts. Although the Convention on International Trade in Endangered Species of Wild Fauna and Flora has banned its export, the fish are still smuggled across the Malaysia–Philippines border.
Four main factors have allowed IUU activities to persist:
- Lack of capacity – a lack exists of formal procedures and personnel to monitor fishing activities and enforce fishing regulations
- Lack of disincentives – Fishers do not have alternatives for the humphead wrasse, due to its value, and sanctions for illegal fishing are not harsh enough to discourage them
- Weak accountability systems – Because a number of people are involved in the species's trade, it is difficult to trace its source; and importers and consumers cannot be held responsible for illegal exportation.
- Absent domestic trade controls – Domestic catching, possession and trade are not sufficiently restricted. Fishers may illegally source the fish or intend to illegally trade it, but cannot be prosecuted if they are in Malaysian waters with appropriate permits.
Most exports of the humphead wrasse in Malaysia occur in Sandakan, Papar and Tawau, where the fish could recently be purchased for between US$45.30 and $69.43, with its retail price ranging from $60.38 to $120.36.
- Green humphead parrotfish (Bolbometopon muricatum)
- Russell, B. (Grouper & Wrasse Specialist Group) (2004). "Cheilinus undulatus". IUCN Red List of Threatened Species. 2004: e.T4592A11023949. doi:10.2305/IUCN.UK.2004.RLTS.T4592A11023949.en. Retrieved 30 December 2019.
- Froese, Rainer and Pauly, Daniel, eds. (2006). "Cheilinus undulatus" in FishBase. April 2006 version.
- Chateau, Wantiez (December 2007). "Site fidelity and activity patterns of a humphead wrasse, Cheilinus undulatus (Labridae), as determined by acoustic telemetry". Environmental Biology of Fishes. 80 (4): 503–508. doi:10.1007/s10641-006-9149-6. S2CID 12829459.
- Weng, Kevin C.; Pedersen, Martin W.; Del Raye, Gen A.; Caselle, Jennifer E.; Gray, Andrew E. (April 29, 2015). "Umbrella species in marine systems: using the endangered humphead wrasse to conserve coral reefs" (PDF). Endangered Species Research. 27 (1): 251–263. doi:10.3354/esr00663. ISSN 1613-4796.
- Sadovy, Y.; Kulbicki, M.; Labrosse, P.; Letourneur, Y.; Lokani, P.; Donaldson, T.J. (September 2003). "The Humphead Wrasse, Cheilinus undulatus: synopsis of a threatened and poorly known giant coral reef fish". Reviews in Fish Biology and Fisheries. 13 (3): 327–364. doi:10.1023/B:RFBF.0000033122.90679.97. S2CID 36840221.
- Sluka, Robert D. (November 2005). "Humphead Wrasse (Cheilinus Undulatus) Abundance and Size Structure Among Coral Reef Habitats in Maldives". Atoll Research Bulletin. National Museum of Natural History (Smithsonian Institution). 538: 192–198. doi:10.5479/si.00775630.538.189.
- Tupper, Mark (2007). "Identification of nursery habitats for commercially valuable humphead wrasse Cheilinus undulatus and large groupers (Pisces: Serranidae) in Palau". Marine Ecology Progress Series. 332: 189–199. Bibcode:2007MEPS..332..189T. doi:10.3354/meps332189.
- Randall, John E.; Head, Stephen M.; Sanders, Adrian P. L. (1978). "Food habits of the giant humphead wrasse, Cheilinus undulatus (Labridae)". Environmental Biology of Fishes. 3 (2): 235–238. doi:10.1007/bf00691948. S2CID 10744732.
- Vail, Alexander L.; Manica, Andrea; Bshary, Redouan (23 Apr 2013). "Referential gestures in fish collaborative hunting". Nature Communications. 4: 1765. Bibcode:2013NatCo...4.1765V. doi:10.1038/ncomms2781. PMID 23612306.
- Dorenbosch, M.; Grol, M.G.G.; Nagelkerken, I.; van der Velde, G. (April 2006). "Seagrass beds and mangroves as potential nurseries for the threatened Indo-Pacific humphead wrasse, Cheilinus undulatusand Caribbean rainbow parrotfish, Scarus guacamaia" (PDF). Biological Conservation. 129 (2): 277–282. doi:10.1016/j.biocon.2005.10.032.
- Poh, Tun-Min; Fanning, Lucia M. (May 2012). "Tackling illegal, unregulated, and unreported trade towards Humphead wrasse (Cheilinus undulatus) recovery in Sabah, Malaysia". Marine Policy. 36 (3): 696–702. doi:10.1016/j.marpol.2011.10.011.
- X.Z. Qi; S.W. Yin; J. Luo; R. Huo (April 10, 2013). "Complete mitochondrial genome sequence of the humphead wrasse, Cheilinus undulatus" (PDF). Genetics and Molecular Research. 12 (2): 1095–1105. doi:10.4238/2013.April.10.5. ISSN 1676-5680. PMID 23661435.
- J. Hu; X.P. Zhu; J. Luo; S.W. Yin; Y.H. Peng; Y.L. Hu; F. Zhu (July 30, 2013). "Development and characterization of microsatellite loci in a threatened marine fish, Cheilinus undulatus (humphead wrasse)" (PDF). Genetics and Molecular Research. 12 (2): 2633–2636. doi:10.4238/2013.July.30.2. ISSN 1676-5680. PMID 23979889.
- Chen, Julia Ng Su; Justin, Spencer Ryan (March 2009). "Regulating the humphead wrasse (cheilinus undulatus) trade in Sabah, Malaysia". Ambio. Springer. 38 (2): 123–125. doi:10.1579/0044-7447-38.2.122. JSTOR 25515818. PMID 19431947.
- Fenner, Douglas (July 15, 2014). "Fishing down the largest coral reef fish species". Marine Pollution Bulletin. 84 (1–2): 9–16. doi:10.1016/j.marpolbul.2014.04.049. PMID 24889317.
- Management of Humphead Maori Wrasse (Cheilinus undulatus) in the Coral Sea Fishery (PDF) (Report). Australian Fisheries Management Authority.
|Wikispecies has information related to Cheilinus undulatus|
|Wikimedia Commons has media related to Cheilinus undulatus.|