Pomachromis fuscidorsalis
A small, uncommon damselfish found around Rarotonga in the Cook Islands and Alofi in Niue, year-round in warm South Pacific water.
A tiny damselfish, topping out around 4 cm, with a pale silvery-white body and a dark grey-brown saddle running along its back and dorsal fin. The tail is usually forked and translucent, giving it a two-tone look that stands out against the darker top half. It hovers in small groups close to the reef rather than out in open water, which helps separate it from bulkier reef fish sharing the same patch.
Look for it hovering in loose little groups just above coral rubble or reef structure, picking at plankton drifting past rather than feeding directly off the substrate. It tends to hold its position rather than bolt when divers approach, though it's small enough to blend into the background and easy to swim past without noticing. Most logs describe it as an uncommon find even at sites where it does occur, so it rewards a slower look at the reef rather than a big-animal sweep.
It's a narrow-range damselfish, with almost all documented sightings clustered around just three South Pacific island groups, making it a real specialty spot for Rarotonga and Alofi divers rather than a fish you'll bump into reef-wide across the tropics.
No clear season shows up in the sighting data, and with a comfortable range of 25 to 29 C it's likely present on these reefs year-round. Plan around general South Pacific dive conditions rather than a specific month.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Rarotonga in the Cook Islands is by far the most reliable place to find it, with Alofi in Niue a solid second option. A handful of sightings also come from the Society Islands in French Polynesia, fitting given the species' Tahitian namesake.
Mapping where Tahiti Damsel is logged…
Rarotonga in the Cook Islands has the strongest run of sightings, with Alofi in Niue a reliable second location. A smaller number of sightings come from the Society Islands in French Polynesia.
There's no detected seasonal pattern in the sighting data, and the water temperature range it's found in (25 to 29 C) holds steady year-round across its South Pacific range, so any month should work.
Look for a tiny damselfish, around 4 cm, with a pale silvery body topped by a dark grey-brown saddle along the back and dorsal fin. It typically hovers in small loose groups close to reef structure rather than swimming far into open water.
They stay small, reaching only about 4 cm as adults, which is one reason they're easy to overlook on a reef full of bigger fish.
It's logged as uncommon even at the sites where it's known to occur, and its range is unusually narrow, concentrated around Rarotonga, Alofi, and the Society Islands rather than spread across the wider tropical Pacific.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Yellowtail Clownfish
3,523 sites
