Yellowtail Blue Damselfish

The Yellowtail Blue Damselfish is a small pomacentrid native to the western Pacific, ranging from the Philippines and Indonesia through Papua New Guinea to the Solomon Islands. It is one of the most recognizable damselfish due to its bicolored blue-and-yellow pattern, and is widely collected for the aquarium trade, though wild populations remain abundant. It typically inhabits shallow, sheltered reef environments such as lagoons and reef flats where branching coral provides cover. As a member of the family Pomacentridae, it shares the group's territorial, hardy nature and small adult size, rarely exceeding about 7 centimeters.

Key features for identifying this species:

• Vivid, almost neon blue coloring covering the head, body, and dorsal/anal fins
• A sharply bordered bright yellow patch covering the rear third of the body and the entire tail fin
• Small, compact, deep-bodied shape typical of Chrysiptera damselfish
• Large, dark eye set high on the head
• Maximum length around 7 cm The crisp, clean line between blue and yellow, and the yellow being confined to the tail region, distinguish it from similar blue damsels.

This species is found on coral reefs throughout the western Pacific, including the Philippines, Indonesia, and Papua New Guinea, at depths of roughly 1 to 12 meters. It favors shallow, current-protected habitats such as lagoons, reef flats, and channels where branching Acropora coral offers dense shelter from predators. Water temperatures across its range stay warm year-round, typically 24-29°C. Juveniles and adults alike stay close to a home coral head, rarely venturing far into open water, making them a reliable indicator species for healthy, structurally complex shallow reef habitat.

Yellowtail Blue Damselfish are highly territorial, especially as they mature, and will aggressively chase off other fish including much larger species from their chosen coral head. Juveniles are often found in loose aggregations over a reef, becoming more solitary or paired as they grow. They feed throughout the day on a mix of planktonic organisms picked from the water column and filamentous algae grazed from rock and coral surfaces. During spawning, males clean a patch of substrate near their territory to attract a female, who deposits an adhesive egg mass that the male then guards and aerates until hatching. Their constant, energetic activity and bold defense of territory make them conspicuous residents of the reef community.