Acanthurus gahhm
Dark, deep-bodied surgeonfish logged as an uncommon find across Marsa Alam and South Sinai reefs in Egypt's warm Red Sea waters.
A deep-bodied, dark grey to almost black fish around 28 cm long, often looking uniformly dusky from a distance with a faint pale patch near the tail base. Look for the sharp little scalpel-like spine at the base of the tail (the feature that gives surgeonfish their name) if it turns broadside. The body is oval and compressed, deeper than most reef fish its length, which helps separate it from similarly dark-toned tangs.
Usually seen alone or loosely associating with other surgeonfish, grazing over rocky and coral substrate rather than schooling in open water. It tends to stay close to the reef structure and keeps a fairly relaxed distance from divers, drifting off rather than bolting if approached slowly. Sightings are logged as uncommon at almost every site, so it is more a case of spotting one grazer among the reef fish than expecting a crowd.
Like other surgeonfish, it carries a sharp, retractable spine at the base of its tail used purely for defence against other fish, not for stinging divers.
Comfortable across a wide 23.8 to 29.1 C range, and the data shows no concentrated season, so treat it as a year-round Red Sea sighting rather than something tied to a particular month.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged in Egypt, especially around Marsa Alam & the Deep South and South Sinai, with a smaller presence across the border in Eilat, Israel. This is very much a Red Sea fish on the current data, so plan your search there rather than further afield.
Mapping where Black Surgeonfish is logged…
Egypt is by far the strongest area, particularly Marsa Alam & the Deep South and South Sinai, with a handful of sites also logged near Eilat, Israel. It sits firmly in the Red Sea corner of divers' logs.
There is no clear seasonal pattern in the sighting data, and it tolerates a broad temperature range from roughly 24 to 29 C, so it is reasonable to expect it on Red Sea reefs any time of year.
No, they are not considered dangerous. Like all surgeonfish they carry a small defensive spine near the tail, but this is used against other fish and poses no real threat if you simply avoid grabbing one.
Look for a deep, oval, dark grey to blackish body around 28 cm long with a faint pale mark near the tail base. The best confirming feature is the small scalpel-like spine at the tail base, shared with other surgeonfish but distinctive of the family as a whole.
They typically reach around 28 cm in length, a solid mid-sized reef fish rather than a small darter, with a noticeably deep, compressed body shape.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Striped Surgeonfish
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