The Humphead wrasse changes markedly in both body form and colouration throughout its lifetime. It occurs widely in the Indo-Pacific, in coastal waters from inshore down to about 100 m. It is found from the Red Sea and African coast, across the Indian Ocean and much of the Pacific, north to southern Japan and the coast of southern China, and south to New Caledonia.
Juveniles occur in coral-rich areas of lagoon reefs, particularly among live thickets of staghorn Acropora sp. corals, in seagrass beds, murky outer river areas with patch reefs, shallow sandy areas adjacent to coral reef lagoons and in mangrove and seagrass areas inshore. They tend to move into somewhat deeper waters as they grow older and larger. However, all adults will regularly visit the shallow drop off areas for reproduction and so adults will often be found in this habitat. Juveniles are all, by definition, sexually immature. It takes quite a long time, possibly up to 5 years, with the fish reaching about 35-50 cm in total length, before individuals attain sexual maturation.
Adults are more common offshore than inshore, their preferred habitat being steep outer reef slopes, reef drop-offs, passes and tops, channel slopes, and lagoon reefs to at least 100 m. They are typically found in association with well-developed coral reefs and may be somewhat sedentary; the same individuals may be seen along the same stretch of reef for extended periods. Indeed, many commercial dive sites have their ‘resident’ Humphead wrasse, a favourite species for divers in many areas.
Population densities are evidently never high, even in preferred habitats. For example, in unfished or lightly fished areas, adult fish densities may range from 2 to 20 (but rarely >10) individuals per 10,000 m2 of reef. This is very low for a commercially targeted reef species and is more akin to densities of large terrestrial animals. In heavily fished areas, the numbers can drop to at least ten times less than in unfished areas. In some countries the species has become rare due to overfishing.
Humphead wrasse feed primarily on molluscs and on a wide variety of invertebrates including crustaceans and echinoderms; heavy shells are crushed with the tough pharyngeal teeth and the species also take fishes. It appears to be one of the few predators of toxic animals such as the crown of thorns starfish, boxfishes and sea hares.
Maximum sizes recorded for this species are from Queensland at 2.29 m (unconfirmed) and 190.5 kg, and 2.5 m and 191 kg. In general, however, fish much larger than 1.5 m are rarely recorded. The reason(s) for this is (are) not clear but it is possible that larger fish are naturally rare, appear to be rare because they are wary, have become rare or occur predominantly in waters deeper than those typically visited by divers, or fished.
The Humphead wrasse can live for at least 3 decades. Age and growth studies using the sagittal otoliths (ear stones) and length data suggest longevity of at least 32 years for females and 25 for males, if the growth checks in otoliths are deposited annually. On the Great Barrier Reef of Australia, fish attain about 1 metre in total length in about 28 years and sexual maturity in about 5 years. Nothing is known of the natural mortality of the Humphead wrasse. The longevity of the species, however, and our limited knowledge of reef fish biology, in general, suggest that adult mortality is low. It is likely, following the early post-settlement period typically associated with high mortality levels in fishes, that natural mortality drops rapidly after fish settle out from the plankton.
This species spawns (reproduces) in pairs formed within larger social groups that form temporary aggregations. Sometimes spawning aggregations can number several hundred fish in unexploited areas; at other times mating groups are much smaller. 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. Population sizes and structures are not yet known for this species.
This wrasse is interesting because some individuals change their sex. Adult females are known to change to adult males, a form of sequential hermaphroditism that is found not only in wrasses but in many reef fishes. We do not yet know what controls the timing of sex change, or how ‘decisions’ are made about which fish change sex. Indeed, we still have much to learn about the biology of this species.
For additional information and photos see:
The humphead wrasse, Cheilinus undulatus: synopsis of a threatened and poorly known giant coral reef fish by Sadovy, Y, Kulbicki M., Labrosse P., Letourneur Y., Lokani, P., and T. J. Donaldson in Reviews in Fish Biology and Fisheries 13(3):327-364). (Note that there is an error in Table 7 in the column for the year 2003 in above paper. The corrected CSD total for January to September is 12,203, the AFCD total is correct at 12,159. All other numbers from the 2003 column should be removed.)
Age structure and growth in a large teleost, Cheilinus undulatus, with a review of size distribution in labrid fishes by J. H. Choat, C. R. Davies, J. L. Ackerman, and B. D. Mapstone.
Aggregation and spawning of the humphead wrasse Cheilinus undulatus (Pisces: Labridae): general aspects of spawning behaviour by P. L. Colin J. Fish Biology Volume 76, Issue 4, pages 987–1007, March 2010.
Forehead morphology of the humphead wrasse Cheilinus undulatus (Perciformes: Labridae) in relation to body size, Copeia 2011: 315-8 by Liu Min and Y. Sadovy de Mitcheson.
Food habits of the giant humphead wrasse, Cheilinus undulatus (Labridae), Env. Biol. Fish. Vol. 3, No. 2, pp. 235-238, 1978 by John E. Randall, Stephen M. Head & Adrian P.L. Sanders.