Yellowtail Blue Damselfish Identification Guide

Key identification features

• Deep, laterally compressed body in vivid electric blue
• Tail (caudal fin) and rear peduncle bright solid yellow, with a sharp, clean boundary between the blue and yellow zones
• Dorsal and anal fins mostly blue, matching the body color
• Small size, typically 2-3 inches (5-7 cm)
• Large dark eye and slightly pointed snout

Common look-alikes

• Blue devil damselfish is solid blue over the entire body and tail, lacking the sharp yellow tail patch.
• Neon damselfish shows only a small yellow smudge at the tail base rather than a fully yellow tail fin.
• Azure damselfish has a similar blue body but a translucent or pale tail rather than solid bright yellow.

Where you'll see one

Yellowtail blue damselfish are found on coral-rich reefs and lagoon patch reefs throughout the western Pacific, especially around Indonesia, the Philippines, and Papua New Guinea. They typically shelter close to branching coral heads such as Acropora, darting into the coral's protective branches when threatened and hovering just above the colony to feed on plankton in the water column.