Hemiglyphidodon plagiometopon
Dusky, territorial reef damsel logged across Sabah, Koh Lipe and Palau all year round in warm 25.5-29.3C water.
Stocky, oval-bodied damsel around 12 cm, coloured dusky brown to olive with a faint pale scallop pattern on the upper body that's easiest to spot in good light. The tail and rear fins often show a darker, almost blackish wash compared with the front half of the body. No bold stripes or eye-spots to key on, so it's really the drab, heavy-bodied shape hugging coral rubble or staghorn thickets that gives it away.
Spend most of a dive parked low in branching coral or rubble patches, darting out to nip algae before retreating to the same perch. Territorial for their size, they'll often chase off other fish, and divers, that get too close to a favoured coral head, especially in the shallows where they're easiest to see. Usually logged as an uncommon to common sighting rather than something schooling in numbers.
Farms and defends small patches of algae on live coral, effectively gardening its own food supply and driving off intruders that threaten the patch.
No clear seasonal pattern in the sightings, and with a comfortable range of 25.5 to 29.3C, it sits on shallow reefs year-round across all these regions.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Most reliably logged in Sabah in Malaysia, and a strong presence around Koh Lipe and Koh Tao in Thailand. Also a common find in Palawan and the Visayas in the Philippines, Java and Bali in Indonesia, and around Koror & Malakal in Palau, with a smaller footprint in New Caledonia.
Mapping where Lagoon Damselfish is logged…
Sabah in Malaysia and Koh Lipe and Koh Tao in Thailand are strong spots, along with Palawan in the Philippines, Java and Bali in Indonesia, and Koror & Malakal in Palau.
There's no strong season in the data. They sit in a warm 25.5 to 29.3C range and are logged on reefs throughout the year.
Look for a stocky, oval damsel around 12 cm, dusky brown to olive with a faint pale scalloped pattern up top and a darker tail. It's usually parked low over coral rubble or staghorn coral rather than swimming in open water.
They top out around 12 cm, a typical small damselfish size that makes them easy to overlook against busier reef scenery.
No. They aren't considered dangerous, though like many territorial damsels they may dart at a mask or hand that strays too close to their patch of coral.
They actively tend small algae patches on live coral, chasing off other fish to protect their own food garden, a behaviour shared with several reef-dwelling damselfish.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Yellowtail Clownfish
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