The Regal Demoiselle (Neopomacentrus cyanomos) is a nonnative species in the Tropical Western Atlantic (TWA) and is a part of the Damselfish family.
Native to the Indo-Pacific, they most likely arrived in the region by hitchhiking on towed oil and gas platforms relocated from their native range (Robertson DR, et al., 2021). It is also possible that they were released from home aquariums.
Looks similar to the Brown Chromis (Chromis multilineata) (native to the Tropical Western Atlantic).
Up to 9cm (3.5 in.) in length.
Dorsal, caudal, and anal fins are streaked with yellow tips at the rear. Upper body and head have a blue-green tint. Lower body has a greyish tint. Body scales have blue markings.
Distinctive spot behind gill cover that can be yellow, black, or both. Bottom of the anal fin is edged bright blue.
May appear more black or greyish underwater.
Click the above photo to expand
(Comparison chart by D. Ross Robertson, Smithsonian Tropical Research Institute)
Depth range of 5-30 meters.
Known to inhabit inshore and offshore coral reefs and common on wrecks and other artificial structures.
Fish eggs, algae, and plankton.
Males are known to guard their eggs and aerate them.
Like other damselfish, adult Regal Demoiselles are territorial.
When mating, the male will clear a site for the female to lay eggs. Males will change colors (become darker, may display white blotches).
Spawning occurs at dawn.
Some experts believe that the nonnative Regal Demoiselle has the potential to place mild competitive pressure on other native reef fish, such as the Brown Chromis (Reef2Rainforest, 2018; Gonzalez-Gandara and de la Cruz-Francisco, 2014; and Johnston, M.W., Akins, J.L., 2016).
How you can help
Help REEF and USGS track the spread of the Regal Demoiselle by submitting a report through the sighting form linked below. If you are doing a REEF fish survey, please report it there too.
More Resources on the Regal Demoiselle
Want to track the spread of the Regal Demoiselle? Check out the USGS Nonindigenous Aquatic Species Tracking Webpage.
For more information check out the video presentations about the Regal Demoiselle by Dr. Ross Robertson of the Smithsonian Tropical Research Institute: