Humphead Wrasse (Napoleon)

The Humphead Wrasse, Cheilinus undulatus, also widely known as the Napoleon Wrasse or Maori Wrasse, is the largest living member of the wrasse family (Labridae) and one of the most iconic and recognizable fish on Indo-Pacific coral reefs.

This charismatic species is renowned for its distinctive appearance and curious nature, often approaching divers with a calm confidence. However, its impressive size and slow reproductive rate make it particularly vulnerable to overfishing, primarily for the live reef food fish trade. Consequently, the Humphead Wrasse is currently listed as Endangered by the IUCN, with populations having declined significantly over the past three decades.

Humphead Wrasses play a crucial ecological role in maintaining reef health. They are one of the few predators capable of consuming hard-shelled invertebrates, including toxic species such as sea hares, boxfishes, and the coral-destroying crown-of-thorns starfish, without being affected by their toxins. They use their tough, fused teeth, resembling a parrot-like beak, to crush prey and can even bite off coral branches or use jets of water to uncover hidden animals.

These magnificent fish inhabit coral reefs throughout the Indo-Pacific region, from the Red Sea and East Africa to the central Pacific, extending north to the Ryukyu Islands and south to New Caledonia. Adults typically prefer steep outer reef slopes, channel slopes, and lagoon reefs, found at depths of 1–100 m, while juveniles often seek refuge among dense branching corals or seagrass beds in shallower areas. While generally solitary, they can sometimes be observed in male-female pairs or small social groups.

Divers frequently encounter Humphead Wrasses at renowned dive sites such as:

• Norman Reef (common)
• SS Yongala (abundant)
• Batu Bolong (occasional)
• Crystal Rock (occasional)
• Black Forest (Balicasag Island) (occasional)
• Shark and Yolanda Reef (common)
• Daedalus Reef (Abu el-Kizan) (common)
• SS President Coolidge (common)
• Blue Hole (Dahab) (occasional)
• Ras Mohammed National Park (occasional)

Identification

• Size: The Humphead Wrasse is truly a giant of the reef, reaching an impressive maximum length of 2.3 m (7.5 ft) and weighing up to 191 kg (421 lbs). Females are generally smaller, rarely exceeding 1 m (3 ft) in length.
• Forehead Hump: Its most distinguishing feature is the prominent, bulbous hump on its forehead, which becomes more pronounced with age and size, particularly in larger males. This hump is the origin of its common names, including "Humphead" and "Napoleon," the latter said to resemble Napoleon Bonaparte's bicorne hat.
• Coloration: Coloration varies significantly with age and sex. Males typically display vibrant shades of electric blue, green, purplish-blue, or dull blue-green. Females and juveniles are generally a red-orange color dorsally, fading to a pale or white ventral surface.
• Facial Markings: Intricate, wavy patterns or "scribbles" adorn the face, particularly behind the eyes and below towards the upper lip. These markings are said to resemble the facial tattoos of the Maori people, giving rise to the "Maori Wrasse" common name.
• Body Shape: Adults have deep bodies, thick, fleshy lips, and a rounded caudal (tail) fin. They possess large scales, often with an elongate dark mark on each scale, which can form a diamond pattern towards the rear of the body in males.
• Locomotion: Like many wrasses, they primarily use their pectoral fins for propulsion, giving them a graceful, almost gliding movement through the water, rather than relying heavily on their tail fin.
• Lifespan: Humphead Wrasses are long-lived fish, with individuals known to survive for at least 30 years, and some females potentially reaching up to 50 years. They are protogynous hermaphrodites, meaning many individuals begin life as females and can transition to males later in life, typically around 9 years of age.

The Humphead Wrasse (Cheilinus undulatus), also known as the Napoleon Wrasse, is a majestic inhabitant of the Indo-Pacific's vibrant coral reef ecosystems. This iconic fish is widely distributed, ranging from the Red Sea and the east coast of Africa across the Indian Ocean to the central Pacific, extending north to the Ryukyu Islands and south to New Caledonia and the Tuamoto Islands.

Its habitat preferences vary with age:

• Juveniles: Younger Humphead Wrasse typically seek refuge in shallower, more protected inshore areas. These include dense coral-rich lagoon reefs, particularly among thickets of branching hard corals like Acropora species, as well as in seagrass beds and areas with bushy macroalgae. They may also be found in shallow sandy areas bordering coral reef lagoons and even inshore mangrove areas.
• Adults: As they mature, Humphead Wrasse move to more exposed, deeper waters. They are predominantly found on steep outer reef slopes, channel slopes, reef passes, and lagoon reefs. These large individuals often patrol the edges of reefs and channels, utilizing caves, crevices, and coral ledges for shelter, especially when resting at night.

Divers can encounter Humphead Wrasse across a significant depth range, typically from 1 to 100 meters. While juveniles are found in the shallower end of this spectrum, adults are commonly observed between 2 and 60 meters, often in areas with abundant hard coral cover. They are diurnal, actively swimming across the reefs during the day in search of prey.

The Humphead Wrasse plays a crucial ecological role as a top predator within its reef ecosystem. Its diet includes a variety of invertebrates such as mollusks, crustaceans, and sea urchins. Notably, it is one of the few predators that consume toxic species like sea hares, boxfishes, and the coral-eating Crown-of-Thorns Starfish, thereby contributing to the health and balance of coral reefs.

The Humphead Wrasse (Cheilinus undulatus), also known as the Napoleon Wrasse or Māori Wrasse, is one of the largest and most iconic reef fish, easily recognized by its prominent forehead hump and thick, fleshy lips. This magnificent species, which can reach up to 2.3 meters in length, is classified as Endangered, making every encounter a special privilege for divers.

Underwater Encounter Behavior

Humphead Wrasses are known for their curious and often docile nature, making them a favorite among the diving community. While often observed cruising slowly and solitarily, they may also be seen in male-female pairs or small social groupings. Unlike many reef fish that flee from divers, Humphead Wrasses frequently approach closely, sometimes even nudging divers with their noses. This inquisitive behavior allows for excellent photo and video opportunities, particularly at dive sites with regular diver traffic where they become habituated to human presence. They are diurnal, active during the day, and seek shelter in reef caves or under coral ledges at night. Adults typically inhabit steep outer reef slopes, channel slopes, and lagoon reefs, at depths ranging from 1 to 100 m, while juveniles prefer shallower, coral-rich areas, often among staghorn corals or seagrass beds.

Feeding Habits

As opportunistic and carnivorous predators, Humphead Wrasses play a crucial role in maintaining the health of coral reef ecosystems. Their diet primarily consists of hard-shelled invertebrates such as mollusks (including sea snails and clams), crustaceans, and echinoderms like sea urchins and starfish. They possess tough, fused teeth, resembling a beak, which they use to pierce shells or break prey away from corals and rocks. A remarkable feeding strategy involves biting off coral branches or blowing jets of water to disturb sediment and uncover hidden prey. They are also one of the few known predators of toxic animals, including sea hares, boxfishes, and the notorious crown-of-thorns starfish, which can devastate coral reefs if their populations are not controlled. Divers have even reported hearing the sounds and seeing clouds of dust created by wrasses demolishing hard corals while feeding.

Social Structure

Humphead Wrasses are generally solitary, but their social structure can include male-female pairs or small groups comprising a dominant male, several smaller adults of mixed sexes, and juveniles. This species is a protogynous hermaphrodite, meaning all individuals begin life as females and can transition to males later in life, typically around nine years of age or when a dominant male is absent. The transition to male often results in increased size, a more pronounced head hump, and vibrant coloration. Dominant males may engage in aggressive displays during spawning, sometimes resulting in scars and split lips from territorial fights.

Notable Seasonal Patterns

Reproduction in Humphead Wrasses involves spawning aggregations, where groups of individuals gather to release gametes into the water column. These aggregations can range from 10 to over 100 individuals and typically occur at specific outer reef locations. While spawning can occur year-round in some locations like Palau, it often shows seasonal and lunar variations, generally coinciding with favorable water temperatures and abundant food. Spawning events usually happen in pairs within the larger aggregation, often a few hours after high tide. Divers may observe these gatherings, which are crucial for the species' reproduction, though their predictable nature also makes them vulnerable to overfishing.