Chaetodon mertensii Cuvier, 1831
Atoll butterflyfish
photo by Randall, J.E.

Family:  Chaetodontidae (Butterflyfishes)
Max. size:  12.5 cm TL (male/unsexed)
Environment:  reef-associated; marine; depth range 0 - 120 m, non-migratory
Distribution:  Pacific Ocean: Ryukyu Islands to the Philippines and extending to Lord Howe, Rapa and Tuamoto islands. Replaced by Chaetodon madagascariensis in the Indian Ocean, Chaetodon xanthurus in southeast Asia, and Chaetodon paucifasciatus in the Red Sea (Ref. 37816).
Diagnosis:  Dorsal spines (total): 12-14; Dorsal soft rays (total): 21-23; Anal spines: 3-3; Anal soft rays: 16-17. Body color is white with 4-5 chevron-shaped blackish bands on the sides. The posterior portion of the trunk, the adjacent dorsal and anal fins, and the posterior portion of the caudal fin are yellow. A vertical black bar runs (uninterrupted) across the eye (Ref. 4855). Snout length 2.3-3.0 in HL. Body depth 1.7-1.8 in SL (Ref. 90102).
Biology:  Inhabit deep lagoons and seaward reefs. Occur singly or in pairs. Feed on algae and small benthic invertebrates (Ref. 1602). Oviparous (Ref. 205). Form pairs during breeding (Ref. 205). May hybridize with C. xanthurus. Minimum depth reported taken from Ref. 128797.
IUCN Red List Status: Least Concern (LC); Date assessed: 09 October 2009 Ref. (130435)
Threat to humans:  harmless


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