Yellowtail Damselfish

The Yellowtail Damselfish is a robust reef damselfish (family Pomacentridae) in the genus Microspathodon, native to the western Atlantic and Caribbean. Juveniles are strikingly marked with iridescent blue spots on a dark body, a pattern that fades to a more uniform dark coloring in adults, while the bright yellow tail persists throughout life. It is one of the larger and more territorial damselfish species in its range, known for aggressively defending algae gardens it cultivates on reef substrate. Wild populations are common and widespread across Caribbean reef habitats.

• Deep, oval, laterally compressed body
• Adults dark blue-black to brown, often with faint remnants of blue speckling
• Juveniles show numerous bright iridescent blue spots across the body and fins
• Consistently bright yellow caudal (tail) fin at all life stages
• Blunt, rounded head profile
• Single long dorsal fin; adults reach 12-17 cm, notably larger than many reef damselfish

Distinguished from similar Caribbean damsels by its larger adult size and persistently yellow tail contrasting with a dark body.

Yellowtail Damselfish inhabit shallow coral reefs, rocky reef zones, and seagrass edges throughout the western Atlantic, from Florida and the Bahamas through the Caribbean to Brazil. They are typically found at depths of 1-20 m in warm tropical water, favoring areas with coral rubble, rock, and algal turf where they establish feeding territories. Juveniles often occupy shallower, more sheltered microhabitats than adults, gradually moving to more exposed reef terrain as they mature.

This species actively cultivates small patches of filamentous algae, called algae gardens, which it defends fiercely against grazers and intruders far larger than itself, including other fish species and even divers. Adults are solitary and highly territorial, while juveniles are more tolerant and often found near cleaning stations or in mixed groups. Its diet includes garden algae supplemented with zooplankton and small invertebrates. Spawning involves males preparing a cleared substrate patch to attract females, after which the male guards and aerates the developing eggs until hatching.