Pomacentrus nigromarginatus
A small dusky damselfish uncommon on Visayas reefs, most reliably logged around West Papua and central Philippines year-round.
A small, deep-bodied damselfish around 6 cm, typically a dusky grey to brownish colour with a noticeably dark, almost black margin running along the edges of the dorsal and tail fins, which is the feature that gives this fish its name. It has the classic damselfish silhouette: compact, slightly flattened side-to-side, with a small mouth built for picking at algae and plankton. Look for it hovering close to coral heads or rubble rather than out in open water.
Divers usually spot this damselfish holding a small patch of reef near coral rubble or low coral heads, sticking close to shelter rather than roaming. It is not a fish that reacts much to divers, staying near its patch and darting for cover in the coral when approached too closely. Given its size and uncommon status at most sites, it rewards a slower, closer look at the reef rather than a fish you spot from a distance.
Like most small pomacentrids, it likely holds a defended feeding territory on the reef, chasing off other small fish that intrude on its patch of algae or substrate.
There is no strong seasonal pattern in the sightings, and it sits comfortably in water between about 24.5 and 28.5 C, so it is a year-round resident on the reefs where it occurs rather than a seasonal visitor.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
This one is most reliably found in the Philippines, especially across the Visayas and Luzon, where the bulk of logged sightings come from. Outside the Philippines it also turns up in West Papua in Indonesia, along the coast around Viti Levu in Fiji, in Milne Bay in Papua New Guinea, and near Dili in Timor-Leste.
Mapping where Black-margined Damselfish is logged…
It is most often logged in the Philippines, particularly in the Visayas and Luzon regions, with additional sightings in West Papua, Fiji's Viti Levu, Milne Bay in Papua New Guinea, and near Dili in Timor-Leste.
There is no clear seasonal pattern in sightings, and the water temperatures it favours, roughly 24.5 to 28.5 C, are typical of these tropical reefs year-round, so it can be seen in any month.
Look for a small, dusky grey damselfish around 6 cm long with a dark margin edging its dorsal and tail fins, usually hovering near coral rubble or low coral heads rather than in open water.
They are small reef fish, typically reaching around 6 cm in length, so spotting one takes a closer look at the reef structure rather than scanning the water column.
No, they pose no danger to divers. They are small, territorial reef fish that may dart at intruders on their patch but present no risk to people.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Yellowtail Clownfish
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