MIDGET CHROMIS (Dwarf Chromis)
Chromis acares Randall & Swerdloff, 1973
    Usually a very rare find in Hawai'i, this small damselfish began to appear in some numbers off the Waianae Coast of O'ahu in June 2017 and was reported off Kauai in July of that year. Previously, it had been known in the Islands from only a few individuals sighted years ago at Kahe Point, O'ahu, and Makena, Maui. Unlike the super-abundant Blackfin Chromis (pictured below), its tail fin margins are yellow and it lacks stripes along the scale rows. Its habits are similar to the Blackfin, and it mixes readily with them. Despite its common name, the Midget Chromis is only marginally smaller than the Blackfin Chromis, attaining 2.25 in. (The Blackfin attains 2.75 in.) It is native to the Western and Central Pacific. Photo taken by Robert F. Myers in Guam.

Chromis acares is common at Johnston Atoll south of Hawai'i, and a few larvae probably drift to Hawai'i from time to time and grow to maturity as isolated individuals. Perhaps enough larvae reached the Islands in 2016 that the species began reproducing here. Or perhaps larvae simply arrived here in unusually large numbers early in 2017 and have now grown up. So far in 2017 Midget Chromis have been seen on Oahu (at Kahe Point and Makua), and on Kauai (at Sheraton Caverns and Koloa Landing). If you see any elsewhere, please let me know! There have been no reports yet from Maui, Lanai, or the Big Island.

Update November 2020: The large numbers of Midget Chromis seen off Oahu in 2017 are gone, though a few are still there. A swarm of larvae must have arrived by chance (probably from the Line Islands), grown to adulthood, and perhaps reproduced in small numbers..

below: Blackfin Chromis for comparison