Stegastes albifasciatus
Small, territorial and easy to miss: find Whitebar Gregory on reef flats around Alofi, Niue and the Society Islands year-round in warm 25-29C water.
A stocky little damselfish, topping out around 9 cm, with a dark brown to blackish body that can look almost sooty in open water. The giveaway is the pale, whitish bar crossing the upper back near the base of the dorsal fin, which stands out against the darker body even at a glance. Juveniles tend to show more contrast and can have a brighter, cleaner look than the duller adults, which fade with age.
Look for it hovering low over shallow reef flats and rubble patches, often close to a patch of algae or coral it is guarding rather than roaming the open reef. It is territorial in a small-fish way, holding its ground against other damselfish and giving divers only a passing glance before returning to its patch. Sightings are logged as uncommon even at sites where it occurs, so expect to spot one or two rather than a crowd.
Like other Stegastes damselfish, it tends to cultivate and defend a patch of algae on the reef, chasing off intruders that try to graze its turf.
No clear seasonal pattern shows up in the sightings, and with a comfortable range of 25.1 to 29.3C it is present on these reefs all year round, so any month works for a visit to its core sites.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
This one is most reliably logged around Alofi in Niue and across the Society Islands in French Polynesia, with a solid secondary population around Tumon Bay and the North Coast of Guam. Smaller numbers turn up at Orchid Island in Taiwan and in Fiji's Yasawa Islands, so it is a Pacific reef-flat specialist rather than a wide-ranging reef fish.
Mapping where Whitebar Gregory is logged…
It is most consistently seen around Alofi in Niue and through the Society Islands of French Polynesia, with further sightings around Tumon Bay and the North Coast of Guam. Smaller numbers are logged at Orchid Island in Taiwan and in Fiji's Yasawa Islands.
There is no strong season in the sightings data, and it sits comfortably in 25 to 29C water year-round, so it can be found on its home reefs in any month.
Look for a small, dark brown damselfish around 9 cm long with a pale whitish bar across the upper back near the dorsal fin. It sits low over reef flats and rubble rather than swimming in open water.
They are small, typically reaching around 9 cm in length, which is fairly standard for a Stegastes damselfish.
No, it poses no danger to divers. It may dart at other fish defending its algae patch, but it has no interest in bothering people on the reef.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
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