Abudefduf abdominalis
Yellow-and-silver damselfish common on Hawaii's reefs at 24-25C, best spotted schooling over shallow rocky reef year-round.
Compact, oval-bodied damselfish around 21 cm with a yellow-green back fading to silvery-white below, crossed by five or six dark vertical bars. The bars are the quickest tell, similar in placement to other sergeant species, but the yellow wash on the upper body is distinctive on Hawaiian reefs. Breeding males darken almost to a deep blue-black over the head and front of the body while guarding eggs.
Usually seen in loose schools grazing over reef flats and rocky slopes, picking at algae and drifting plankton in the water column. It holds its ground around divers rather than bolting, and is most often noticed hovering just off the bottom in good light rather than tucked into crevices. Around egg-laying time, individual males turn dark and patrol a patch of reef aggressively, chasing off anything that gets too close to their nest.
Males guard a patch of eggs laid on bare rock, darkening in colour and fanning the clutch, which makes territorial nesting males one of the more distinctive behavioural sightings on a Hawaiian reef dive.
Sightings show no clear seasonal pattern, and with water temperatures logged in a narrow 24 to 25.5 C band, it is a year-round fixture on Hawaiian reefs.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
This is a Hawaii speciality, logged across reef sites throughout the archipelago from Oahu to the Big Island, with no other regions showing meaningful numbers in diver reports. If you are diving Hawaiian waters, expect to run into it on shallow reef and rocky drop-offs rather than needing to seek out a specific site.
Mapping where Hawaiian Sergeant is logged…
Almost entirely a Hawaii sighting, reported across reef sites throughout the state from Oahu to the Big Island. It is one of the most frequently logged reef fish in Hawaiian waters.
No strong season shows up in diver logs, and the water stays a steady 24 to 25.5 C, so it is present on Hawaiian reefs all year round.
Look for a yellow-backed, silver-bellied damselfish about the size of your hand, marked with five or six dark vertical bars. Nesting males turn almost black over the head and front half of the body.
They grow to around 21 cm, a medium-sized damselfish easily spotted schooling over shallow reef.
No. They are harmless to divers, though a nesting male may dart at your mask or hand if you get too close to its egg patch.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Yellowtail Clownfish
3,523 sites
