Allen's Damselfish Identification Guide
Spot Allen's Damselfish by its neon blue body, black dorsal stripe, and bright yellow tail.
Read the full Allen's Damselfish encyclopedia entry →
Key identification features
- Small damselfish, typically under 6 cm (2.4 in)
- Bright neon blue body covering the head and most of the flanks
- Thin black stripe running along the base of the dorsal fin
- Sharp-edged yellow patch covering the rear body and tail
- Large dark eye and a slightly forked tail fin
Common look-alikes
- Azure Damselfish: similar blue-yellow split, but lacks the black dorsal-fin stripe and shows a more abrupt color division
- Yellowtail Damselfish: blue body, but yellow is restricted to just the caudal fin rather than the rear third of the body
- Springer's Damselfish: shows a dark saddle blotch near the tail base instead of a clean color split
Where you'll see one
Allen's Damselfish is found on coral-rich reef slopes and lagoons of the Coral Triangle, from the Philippines through Indonesia to Papua New Guinea, usually hovering close to branching coral for shelter in depths of a few to 20 meters. It is frequently seen in small aggregations picking plankton just above the coral canopy.
Frequently asked questions
What single feature separates Allen's Damselfish from the similarly colored Azure Damselfish?
The thin black stripe running along the dorsal fin base — Azure Damselfish lacks this stripe entirely.
Where is the yellow located on Allen's Damselfish compared to lookalikes?
It covers the entire rear third of the body and tail with a sharp edge, not just the tail fin as in the Yellowtail Damselfish.