The Steephead parrotfish (Chlorurus strongylocephalus) is also known as the Roundhead Parrotfish. Parrotfish obtain their name from their teeth which are fused into a beak. This species is part of a complex of species along with Chlorurus gibbus from the Red Sea and Chlorurus microrhinos which is found in the west-central Pacific.
Within the various species of Parrotfish which are part of the Labridae family there is considerable divergence in looks between the juveniles and the adults and some females based on social cues change into so called Supermales which are very colorful. Additionally there are regional variations in looks which seem to be great in this species because the males in Tanzania seem to have different colors to those from elsewhere. This combined with their ability to change their colors particularly at night to some degree, creates a large amount of confusion as to which species is which. To put this into perspective in 1956 Schultz recognised 57 species in the West Indian ocean alone and today there are 29.
Most have been described on multiple occasions in various areas with this species having been described on at least three occasions by different scientists in different parts of the world. It can often be exceedingly difficult to determine which species is which. As one can see below in chronological order of growth the changes are dramatic. These images will only be indicative of color patterns for Tanzania.
In Tanzania the small juveniles start out as above with dark brown black and yellow stripes. They then grow into the pattern below being a light brownish yellow color with yellow caudal, anal and dorsal fins that are lightly edged in blue. Even at this age the head is noticeably rounder than other species of parrotfish its size.
As they age so blue lines develop around the mouth and blue develops on the mid section of the caudal fin.
With further growth these features become more prominent and a blue circle develops around the eye. The body begins to lighten from the head and tail going more yellow.
Eventually they mature into an initial phase as seen below. The body is predominantly yellow with darker orange scale edges in the lower mid body. With the yellow and blue edging they make a very attractive Steephead parrotfish.
Some females, probably the larger more dominant ones, driven by social cues change into males as pictured below, becoming very colorful. The lower cheek initially stays yellow and the upper head and the bulk of the body go a dull light purple color which brightens as one moves onto the caudal area. Lines develop around the eye and running along the dorsal and anal fins. All in all a stunning looking fish. The tail begins going slightly lunate and filaments develop on the outer rays.
The males grow up to 70 cm although these are today extremely rare and usually only seen in marine parks. A large male of this size is pictured below. Some yellow has developed on the rear back towards the caudal area and the filaments on the caudal fin have lengthened substantially. A stunning looking Steephead parrotfish. in Tanzania likely only to be seen in the Marine Park on Mafia Island where this specimen was photographed or on remote reefs.
STEEPHEAD PARROTFISH IN THE WILD
As a juvenile the Steephead parrotfish can be seen feeding on the shallower reefs at around 10 to 15 meters with groups of Rabbitfish , Goatfish, Wrasse and smaller Surgeonfish. They are fairly rare and are not common in Tanzania. They are always seen solitary and we have never seen more than one at a time. The younger males are occasionally seen around 15 meters but the large adults we have only seen around 25 meters.
The Steephead Parrotfish is found from Mozambique northwards up the East African coast up to the Gulf of Aden and across to Western Indonesia.
The Steephead Parrotfish as with most other parrotfish feed on a variety of filamentous algae which is scraped off dead coral using their powerful beaks. These scrapings which are mainly comprised of inorganic matter are further ground down by bony teeth plates and then go into a long specialized alimentary canal where nutrients are extracted. The inorganic matter is expelled as fine sand.
Steephead 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.
Individual pairing takes place and the eggs are released into the substrate. Interestingly in a genetic study done in the Philippines in three different areas full siblings and half siblings were found at sites more than 500 km apart. This indicates that the eggs or larvae are widely distributed by the currents.
Steephead Parrotfish are not commonly kept in aquariums although some public aquariums may occasionally keep them for public display. This is both a function of their size and the difficulty in providing them with food.
All the Parrotfish are heavily exploited in Tanzania both by trapping and netting. Parrotfish carry a heavy premium on price, and make very good eating as a rule.