Humphead parrotfish  (Bolbometopon muricatum)

Classified as Vulnerable (VU) on the IUCN Red List 2007 (1).

The largest of all parrotfish, the humphead parrotfish is an olive or blue-green to slate-grey fish, with a yellowish to pink head (2). Its most distinctive feature, and the reason for its common name, is the prominent bulbous forehead which develops in adults (2). Juvenile humphead parrotfish do not have this bulging head and also differ slightly in colour, being green or brown with five vertical rows of small, whitish spots (2). Parrotfish get their name from their peculiar teeth, which are fused into a parrot-like beak. They also have teeth at the back of the throat which grind food (3).

The humphead parrotfish can be found in tropical and subtropical coral reefs in the central and western Pacific, Indian Ocean and Red Sea (2).

This coral reef fish inhabits shallow fringing and barrier reefs, between depths of one and thirty metres (1) (2). While adult parrotfish are most often found in outer lagoons and seaward reefs, juveniles are more often found inside lagoons, in seagrass beds (4). At night, this parrotfish can be found resting in caves or on the sandy flats of shallow lagoons (2).

The gregarious humphead parrotfish is always found in small shoals, sometimes consisting of up to 75 individuals (1). It feeds on a diet of live corals and algae that grow on the ocean bottom, and uses its large bulbous head to ram the coral to break it into smaller, more easily digested pieces (1). Its beak-like front teeth and pharyngeal teeth at the back of the throat adeptly grind down this food, reducing the hard coral to a paste and breaking down the algae (3). Any hard, un-nutritious material is passed out in the fish’s faeces (3). As a consequence, adult humphead parrotfish, which are estimated to consume five to six tonnes of coral each year, produce substantial amounts of sediment and influence the structure of coral reefs, thus playing an important role in the coral reef ecosystem (2).

Humphead parrotfish aggregate to spawn at a certain time each month, often around the time of the full moon, in reef channels and passages. Spawning often takes place in early morning (2) (5), when females release eggs to be fertilized in the water by the sperm released by the male. These large spawning aggregations may consist of around 100 individuals. Large groups of humphead parrotfish are also found when they are sleeping. These large fish can live to an age of at least 40 years (1).

The habit of feeding, resting and spawning in groups makes the humphead parrotfish highly vulnerable to fishing, particularly by spear-fishing during the night (1) (2). This has resulted in a decline in numbers of the humphead parrotfish in some areas (1), and this once abundant fish is now virtually extinct in Guam, the Marshall Islands, parts of Fiji and East Africa (2).

There are no protective measures specifically in place for the humphead parrotfish (1), but a number of fishing regulations should afford this vulnerable fish some protection (2). For example, in some regions, restrictions on night-time spear-fishing or spear-fishing with compressed air are in place (1) (2), measures which will help protect the parrotfish when it is at its most vulnerable. Marine Protected Areas (MPAs), in which fishing is prohibited, protects numerous species; two MPAs were established in the Solomon Islands in 2002 (Baraulu Village and Nusa Hope Village) to protect the humphead parrotfish and other reef species (1).

For further information on the humphead parrotfish see:

• IUCN Red List:
  www.iucnredlist.org

• Algae: simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
• Barrier reefs: barrier reefs are separated from the mainland or island shore by a deep lagoon.
• Fringing: a fringing coral reef is one that forms close to the shoreline.
• Pharyngeal: to do with the pharynx or throat.
• Spawning: the production or depositing of large quantities of eggs in water.

1. IUCN Red List (January, 2008)
   http://www.iucnredlist.org/
2. Donaldson, T.J. and Dulvy, N.K. (2004) Threatened fishes of the world: Bolbometopon muricatum. Environmental Biology of Fishes, 70: 373 - .
3. Australian Museum Fish Site (May, 2008)
   http://www.austmus.gov.au/fishes/index.cfm
4. NOAA Fisheries. (2007) Species of Concern Factsheet: Bumphead Parrotfish. NOAA Fisheries, Office of Protected Resources, USA. Available at: http://www.nmfs.noaa.gov/pr/species/
5. Hamilton, R.J., Adams, S. and Choat, J.H. (2008) Sexual development and reproductive demography of the green humphead parrot (Bolbometopon muricatum) in the Solomon Islands. Coral Reefs, 27: 153 - 163.