Plectroglyphidodon gascoynei
A dusky little damselfish patrolling reefs in New South Wales and Queensland, comfortable in 21.6 to 27.1C water year-round.
A small, deep-bodied damselfish reaching about 10 cm, usually seen in dusky brown to dark grey tones that blend into the reef backdrop. Look for the compact, oval profile typical of damselfish and its habit of staying tight to a chosen patch of reef or rock rather than roaming. There is no strong colour contrast or bold stripe to key on, so its plain, shadowy look combined with its territorial hovering is itself the giveaway.
Divers typically find it holding a small patch of reef or rocky bottom, hovering close to shelter rather than swimming out into open water. It is not bold or attention-seeking around divers, tending to stay low and slip back toward cover if approached too directly. Like most damselfish it is territorial in a quiet way, defending its patch from other small fish rather than from divers.
It belongs to a genus of small, strongly territorial reef damselfish, and individuals often guard the same patch of rock or coral rubble across repeated dives, so a site where you spot one once is worth checking again.
No clear seasonal pattern shows in the sighting data, and its comfort range of 21.6 to 27.1C spans both cooler temperate and warmer subtropical conditions, so it is worth looking for on any dive through the year at these sites.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged on reefs in New South Wales, Australia, with a strong secondary presence in Queensland, Australia. A small number of sightings also come from Norfolk Island, making it a useful species to look for on that island's reef edges.
Mapping where Coral Sea Gregory is logged…
It is most consistently logged on reefs in New South Wales and Queensland, Australia, with additional sightings from Norfolk Island. It is considered uncommon even at the sites where divers do find it, so treat any sighting as a bonus rather than a guarantee.
There is no detected seasonal pattern in sightings, and it tolerates a fairly wide temperature range of 21.6 to 27.1C, so it can turn up on dives at any time of year at the sites where it occurs.
Look for a small, oval-bodied damselfish around 10 cm long in plain dusky brown or grey tones, holding position close to a patch of reef or rock. It lacks bold stripes or bright colour patches, so its unremarkable, shadowy look paired with territorial hovering behaviour is the main clue.
They reach roughly 10 cm in length, putting them firmly in the small end of the damselfish family.
No. They pose no danger to divers and are not aggressive toward people, though like other damselfish they may act territorially toward other small reef fish.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Yellowtail Clownfish
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