The humphead wrasse, scientifically known as Cheilinus undulatus, is a notable species of wrasse primarily found in the Indo-Pacific region, specifically on coral reefs. This species is also referred to as the Māori wrasse, Napoleon wrasse, Napoleon fish, so mei 蘇眉 (Cantonese), mameng (Filipino), and merer in the Pohnpeian language of the Caroline Islands.
As the largest living member of the labridae family, male humphead wrasses can reach impressive sizes, measuring up to 2 meters in length and weighing up to 180 kg. However, the average length for this species is slightly less than 1 meter. Females, on the other hand, rarely grow larger than one meter. Distinguishing characteristics of the humphead wrasse include its substantial size, thick lips, two black lines behind its eyes, and the prominent hump on the foreheads of larger adults. The coloration of this species can vary, ranging from dull blue-green to more vibrant shades of green and purplish-blue. While adults are often observed living alone, they can also be found in male/female pairs or small groups.
The humphead wrasse inhabits various regions, including the east coast of Africa around the 🌊 Red Sea, as well as certain areas of the 🇮🇳 Indian and 🌊 Pacific Oceans. Juveniles prefer shallow, sandy ranges adjacent to coral reef waters, while adults predominantly reside in offshore and deeper sections of coral reefs, typically on outer-reef slopes and channels, and sometimes within lagoons.
With a long lifespan and slow breeding rate, the humphead wrasse matures sexually between five to seven years of age and is known to live for approximately 30 years. They exhibit protogynous hermaphroditism, with some individuals transitioning to the male sex around nine years old. However, the precise factors governing sex change timing are not yet fully understood. These fish congregate in local spawning aggregations during certain times of the year, typically moving towards the down-current end of the reef. Their spawning aggregations likely occur relatively close to their usual habitats. The pelagic eggs and larvae eventually settle on or near coral reef environments. The eggs are spherical, measuring 0.65 mm in diameter and lacking pigmentation.
The humphead wrasse possesses an opportunistic predatory nature, primarily preying on invertebrates such as molluscs (particularly gastropods), pelecypods, echinoids, crustaceans, and annelids, as well as other fish, including poisonous sea urchins and crown-of-thorns starfish. Can be toxic. In their search for prey, they may rely on fish excavators like stingrays or adopt excavation techniques themselves by expelling water to displace sand and uncover potential prey. Similar to other wrasses in the 🌊 Red Sea, humphead wrasses have been observed cracking open sea urchins (echinoids) by carrying them in their mouths and striking them against rocks using brisk, sideways head movements. They sometimes engage in cooperative hunting with the roving coral grouper. Adults are commonly found in steep coral reef slopes, channel slopes, and lagoon reefs, typically at depths ranging from 1 to 100 meters (3 to 330 feet).
During the settlement phase, this species actively selects branching hard and soft corals, as well as seagrasses. Juvenile humphead wrasses tend to prefer cryptic habitats, residing in areas with dense branching corals, bushy macroalgae, or seagrass beds. In contrast, larger individuals and adults favor more open habitats on the periphery of reefs, channels, and reef passes, establishing limited home ranges.
Why it's threatened
Threat classification from the IUCN Red List.
