The Swarthy Parrotfish (Scarus niger) is also known as the Dusky Parrotfish and the Black Parrotfish. As with all the Parrotfish which are part of the Labridae family there is considerable divergence in looks between the juveniles and the adults. Parrotfish obtain their name from their teeth which are fused into a beak.
There are several distinct coloration changes and then variations between the changes often making it extremely difficult to identify parrotfish. To make it even more difficult they are able to substantially vary their colouration, particularly at night for camouflage purposes. To make it even more difficult there are regional variations and some females change into males which are very brightly colored. These are known as Supermales.
SWARTHY PARROTFISH APPEARANCE
The juvenile Swarthy Parrotfish pictured below has a dark green black body with a lighter green section across the dorsal area around the front of the body. There are lines of blue dots running horizontally across the body and there is usually but not always a white bar in the caudal area.
From the juvenile stage the Swarthy Parrotfish morphs into the initial stage which is pictured below. Depending on the age of the particular specimen, there are many variations between the two stages.
In this stage , termed the Initial Phase or IP, the lower facial area down to the pelvic fin reddens and the lines of dots on the rear of the body morph into broken blue lines. The caudal, anal, pectoral and rear of the dorsal fin are blue. Note the beak is also blue at this stage.
From the Initial Phase above, the Swarthy Parrotfish grows into the adult phase or Terminal Phase ( TP)pictured below in the beginning stages. From here onwards they actually become relatively easy to identify. This because of the irregular horizontal line behind the eye which is usually green with a yellow mark at the end.
The front of the body is an orange brownish colour and the main part of the body behind the gills has a green cross hatched pattern on it. The caudal fin is a pinky colour with a blue ringed yellow green square on it. The area above the mouth is orange with a green line across it. The dorsal fin is orange lined in blue.
In the final part of the terminal phase pictured below, the body darkens into a dark brown black color with a green sheen to it . The dorsal fin is orange lined with blue, the caudal and anal fins are redish lined in blue and the green line behind the eye is far more prominent because of the darkened body.
The pectoralfin is a purple color. The beak is blue and the area above and just behind the mouth is orange with green lines across the face.
To further complicate identifying the Swarthy Parrotfish, as can be seen in the image of an adult taken below at night , they are able to modify their colouration substantially. If it were not for the green line behind the eye one might have difficulty identifying it. It is assumed that each stage is similarly capable of modifying their colouration.
SWARTHY PARROTFISH IN THE WILD
The Swarthy Parrotfish is fairly common in Tanzanian waters. The juveniles are far more common than the adults, presumably as a result of being overfished. It is fairly rare to see a fully developed adult male and they seem to be very reclusive on the mainland coast. T
he juveniles and adults are usually seen on mixed rubble and coral flats from 8 to 20 meters. They have a maximum recorded age of 18 years and are usually seen solitary as adults. Sometimes the juveniles are seen in small groups of two or three. It is quite possible that the Indian Ocean and Pacific specimens are a separate species, however more research is necessary to prove this.
SWARTHY PARROTFISH HABITAT
The Swarthy Parrotfish is found across the Indian Ocean from East Africa across into the Pacific as far south and east as the Great Barrier Reef and the Pacific Islands. They are found as far north as the Ryuku Islands south of Japan.
The Dusky 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.
SWARTHY PARROTFISH REPRODUCTION
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.
SWARTHY PARROTFISH AQUARIUMS
Dusky 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, particularly the blue parrotfish. They make very good eating as a rule.