Pycnochromis vanderbilti
A small silvery damselfish most reliably spotted on Hawaiian reefs in 22-29C water, year-round and easy to overlook.
A slim, torpedo-shaped damselfish that tops out around 4 cm, so it's easy to miss among bigger reef fish. Body colour runs pale silvery-grey to bluish, often with a faint dark smudge near the base of the tail and a forked tail fin. It swims in loose, open-water groups just off the reef rather than hugging structure, which is often the first clue you've found one.
Typically seen hovering in small, loose aggregations a short distance above the reef, picking at drifting plankton in the water column rather than feeding off the substrate. It shows little concern for divers, generally holding its position or drifting off unhurried rather than darting for cover. Most sightings are logged as uncommon rather than common, so expect to actively scan mid-water rather than find it parked in one obvious spot.
Like other chromis, it feeds mainly by snatching plankton out of open water, which is why you'll usually see it holding station above the reef rather than picking through the coral itself.
No clear seasonal pattern shows up in the data, and with a comfortable range of 22.3 to 29.3C it's present on Hawaiian reefs year-round. Plan around good general dive conditions rather than a particular month.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Sightings cluster overwhelmingly in Hawaii, with reefs across the islands producing the vast majority of logged encounters, and it's been recorded far more sparingly at Lomaiviti in Fiji. If you're diving Hawaiian sites, keep an eye on open water just off the reef edge, where it tends to hang in loose groups rather than tucked into coral.
Mapping where Vanderbilt's Chromis is logged…
It's most reliably seen on reefs across Hawaii, with occasional records from Lomaiviti in Fiji. Hawaii accounts for the large majority of logged sightings, so it's very much a Hawaiian reef regular.
There's no strong season in the sighting data, and its comfortable temperature range of roughly 22 to 29C means it's present on Hawaiian reefs throughout the year.
Look for a small, slender silvery-grey to bluish damselfish around 4 cm long, hovering in loose groups off the reef edge rather than sheltering in coral. A forked tail and a subtle dark mark near the tail base help separate it from similar chromis.
They're small, typically reaching around 4 cm in length, making them one of the more easily overlooked damselfish on a reef.
No, they pose no threat to divers. They're small plankton feeders that mostly ignore divers entirely.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Yellowtail Clownfish
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