Parrotfish are a group of about 90 species traditionally regarded as the family Scaridae. Today they are considered to be in Scarinae a subfamily of wrasses.
Parrotfish are found in coral reefs, rocky coasts, and seagrass beds in relatively tropical and subtropical oceans throughout the world. They are however most abundant in the Indo-Pacific.
They have numerous teeth arranged in a tightly packed mosaic on the external surface of their jaw bones. These form a parrot-like beak from which their name derives. The beak is used to eat algae from coral and other rocky substrates. This contributes to the process of bioerosion.
Generally they are extremely colorful and although the largest, the green humphead parrot fish can grow up to 1.3 meters, they are generally in the 30 to 50 cm range. Parrotfish are unusual in that they have the ability to change their sex throughout their lifetime.
At birth both males and females are present and these are referred to as primary males and females. The primary males and females are less colorful and are often difficult to tell apart. Secondary males are born female and change their sex when prompted by social cues such as the absence of another secondary male. These secondary males are often referred to as Supermales because of the brightness of their colors.. The juveniles usually bear no resemblance to the adults.
During the night parrotfish wedge themselves into small cracks and some species secrete a white colored mucus around themselves. This is thought to mask their scent from predators and to possibly provide an early warning system when touched by predators. The taste of the mucus may also deter predators.
They are pelagic spawners and during spawning the eggs are released into the water table. They then float down onto the substrate where they hatch. The young often form small groups of three or four. They often form small shoals with juvenile goat fish.
Although, parrotfish are considered to be herbivores, they eat a wide variety of reef organisms, and they are not necessarily vegetarian. Species such as the humphead parrotfish (Bolbometopon muricatum) include coral polyps in their diets. Their feeding activity is important for the production and distribution of coral sands in the reef biome. Their feeding habits also prevent algae from choking coral.
Parrotfish teeth grow continuously, replacing material worn away by feeding. After digesting the edible portions from rock and corals, they excrete it as sand. This helps to create small islands and sandy beaches. One parrotfish can produce 90 kg (200 lb) of sand each year.