The humphead wrasse ( Cheilinus undulatus), also known as the Māori wrasse, napoleon wrasse, and napoleonfish, is a large and distinctive species of wrasse primarily inhabiting coral reefs throughout the Indo-Pacific region. This article delves into the dietary habits of this fascinating and endangered fish.
Physical Characteristics and Distribution
The humphead wrasse is the largest extant member of the Labridae family. Males, typically larger than females, can reach up to 2 meters in length and weigh as much as 180 kg, though the average length is a little less than 1 meter. Females rarely grow larger than one meter. The species is easily identified by its large size, thick lips, two black lines behind its eyes, and the prominent hump that develops on the foreheads of larger adults. Its color varies from dull blue-green to more vibrant shades of green and purplish-blue. These wrasses are found on the east coast of Africa around the mouth of the Red Sea, and throughout areas of the Indian and Pacific Oceans.
Habitat and Behavior
Adult humphead wrasses 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. Occupying limited home ranges, the adults swim across the reefs during the day, resting at night in caves and under coral ledges. Juveniles select branching hard and soft corals and seagrass beds at settlement.
Dietary Habits
Humphead wrasses are very opportunistic predators. Prey items comprising the humpback wrasse’s diet include mollusks, sea urchins, crustaceans, and fishes. These large reef fish have tough teeth fused into a parrot-like beak, enabling them to consume hard-shelled species including mollusks, echinoderms and crustaceans. The pharyngeal teeth, a second set of dentition located inside the fish’s throat, enable the fish to crush prey items. Specifically, C. undulatus preys primarily on invertebrates such as mollusks (particularly gastropods, as well as pelecypods, echinoids, crustaceans, and annelids) other fish, and even the highly venomous Crown-of-thorns starfish. Some of these prey items are toxic such as sea hares, and boxfishes.
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.
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Conservation Status and Threats
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. The pelagic eggs and larvae ultimately settle on or near coral reef habitats.
Unsustainable and severe overfishing within the live reef food fish trade is the primary threat. Sabah, on Borneo Island, is a major source of 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.
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.
Conservation Efforts
In 1996, following a decade of rapid population decline, the humphead wrasse was placed on the IUCN Red List of endangered species.
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, which issues permits to regulate fishing activity. 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. In 2003, Australia prohibited the take and possession of this species other than for some educational uses and public display. Other countries including the Philippines, Maldives, and Palau have enacted some protective regulations as well.
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Illegal, unregulated, and unreported activities have been identified as the major factor for the failure of conservation efforts. Absent domestic trade controls - Domestic catching, possession, and trade are not sufficiently restricted.
Importance to Ecosystem and Humans
The humphead wrasse is a species commonly exhibited in public aquarium facilities and is considered of importance to eco-tourism in areas frequented by divers. Traditionally the flesh of this fish has been highly regarded for human consumption; it is often found alive in the fish markets of Hong Kong fetching prices up to $100 US per kilogram. Eating this fish has resulted in cases of ciguatera poisoning.
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