Yellowtail Damselfish in Cozumel

Adults are dark brown-blue with a bright yellow tail. Juveniles — often called jewelfish — are deep blue scattered with brilliant electric blue spots.

Quick ID

Where You Will See It In Cozumel

Shallow coral and fire coral at Paradise Reef, Chankanaab and Playa Corona, each fish holding a small patch.

Reliable sites: Paradise Reef, Chankanaab Reef, Playa Corona.

Behaviour

Fiercely territorial farmers. They cultivate patches of algae, weed out the species they do not want, and charge fish many times their size — including divers who hover too long over the patch.

Commonly Confused With

• Other damselfish — The bright yellow tail on a dark body identifies the adult; the electric blue spots identify the juvenile.
• Blue chromis — Blue chromis are slender, bright blue and school in open water.

Diving Etiquette And Safety

Nothing required beyond amusement. A damselfish charging your mask is defending a patch of algae, not attacking.

Part of the Cozumel marine life guide · see Cozumel dive sites · plan your Cozumel dive trip

Photo: Paul Asman and Jill Lenoble, CC BY 2.0, via Wikimedia Commons.