Pomacanthus imperator Bloch, 1787, Japan.
OTHER COMMON NAMES
Afrikaans: Keiser-engelvis; French (Polynesia): Poisson empereur; paraharaha; Japanese: Tatejima-kinchakudai.
Deeply compressed, with longish pelvic fins and a long preopercule spine. Adults and juveniles have distinct color phases. Adults are yellow with horizontal blue stripes along the flank, a deep purplish mask over the eye and on the flank above the pectoral fin, a white snout and mouth, and yellow fins with purplish blue stripes on the anal fin. Juveniles are deep navy blue to almost black, with concentric white circles on the flank and white bands on the head. One of the largest angelfishes, to over 15.7 in (40 cm) total length.
Red Sea east to the Line Islands and the Tuamotu Archipelago; southern Japan south to northern Australia, and southeast to Lord Howe Island and the Austral Islands. Reported from Hawaii, but either very rare as a stray or introduced from aquarium stock.
Coral reefs. Juveniles on patch reefs in lagoons, protected areas in lagoon passes, and among corals, in holes or under ledges on outer reefs or reef flats; subadults move to surge channels and holes on reef fronts; and adults are found usually near caves and ledges of seaward reefs, passes, or lagoons.
Usually observed paired or singly as they patrol a large home range; may display some intra- or interspecific territorial
(usually towards other similarly sized angelfishes). Have an haremic mating group, with subordinate females residing within the male’s home range.
FEEDING ECOLOGY AND DIET
Feed almost exclusively on sponges and tunicates.
Protogynous hermaphrodites. Sequential courtship and spawning among members of a mating group occur at dusk. Eggs and larvae are pelagic. Eggs are round, approximately 0.023–0.039 in (0.6–1 mm) in diameter. Larvae hatch around 0.05–0.1 in (1.3–2.6 mm) in length, have a large yolk sac, an unformed mouth, and unpigmented eyes. With growth, they assume a deep, laterally compressed shape, and the profile of the head becomes steep. Possesses a gas bladder. The development of head spination and spinules (spine-like structures on the skin) are specializations for pelagic life.
Not listed by the IUCN. Because of apparent low population densities at many localities, this species is subject to overfishing by the aquarium trade.
SIGNIFICANCE TO HUMANS
Highly prized, especially the juveniles, as an aquarium fish. Adults are also taken occasionally in subsistence food fisheries.
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