Acanthurus pyroferus
A reef regular across the Visayas and Society Islands, easy to overlook at 25-29C but worth learning to spot on any Indo-Pacific reef.
A stocky, oval-bodied surgeonfish around 20 cm, uniformly dark chocolate-brown to almost black over the whole body, with a small pale to orange patch near the base of the tail that catches the eye first. Look for the sharp spine folded into a groove at the tail base, the tell-tale weapon of all surgeonfish, though it is rarely on display. Juveniles are a completely different story: they mimic the yellow body and blue-outlined face of certain angelfish, changing colour as they mature into the plain brown adult form.
Usually seen alone or loosely associating with other surgeonfish, grazing algae off dead coral and rock in the shallows to mid-reef. It is not a fish that reacts much to divers, generally holding its feeding line and drifting off at an unhurried pace rather than bolting. Most sightings come from open reef flats and slopes rather than caves or walls, at any time of day when the light is good enough to feed.
Juveniles closely mimic the colour pattern of certain dwarf angelfish, a disguise thought to help them slip past territorial adult angelfish and predators while they are small and vulnerable.
No clear seasonal pattern shows up in the sighting data, and with a comfortable range of 25 to 28.8C on tropical reefs, it is a year-round find wherever it occurs.
Most reliably logged in the Philippines, especially the Visayas, and across Indonesia in Bali, Sulawesi, Nusa Tenggara and Raja Ampat. French Polynesia's Society Islands hold a strong population too, with further sightings in Vanuatu's Efate, Fiji's Taveuni, Taiwan, Guam and Australia.
Mapping where Chocolate Surgeonfish is logged…
It turns up widely across the Indo-Pacific, most commonly in the Philippines' Visayas region, throughout Indonesia (Bali, Sulawesi, Raja Ampat), and in French Polynesia's Society Islands. Smaller but reliable populations exist in Vanuatu, Fiji, Taiwan and Guam.
There is no strong seasonal pattern in the sightings, so it is a fair bet year-round on any warm Indo-Pacific reef sitting between 25 and 29C.
Look for a plain dark brown, oval-shaped fish about 20 cm long with a pale patch near the tail base. The lack of stripes or bold patterning is itself the giveaway among the more flashy surgeonfish it shares reefs with.
They typically reach around 20 cm in length, a modest mid-sized surgeonfish that blends easily into mixed grazing groups on the reef.
Juveniles wear a yellow body with blue facial markings that closely mimics certain dwarf angelfish, likely a form of protective disguise. As they grow they lose this pattern and settle into the uniform brown of the adult.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Striped Surgeonfish
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