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 fertilised 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).