Bicolor Damselfish in Cozumel
Bicolor Damselfish (Stegastes partitus) in Cozumel: how to identify it, where it is reliably seen, and what it is commonly confused with.
Dark at the front, pale at the back, and completely out of proportion in attitude to its size. Bicolor damselfish defend a patch of reef against anything, divers included.
Quick ID
| Scientific name | Stegastes partitus |
|---|---|
| Group | Colourful Reef Fish |
| Typical size | Up to 10 cm |
| Depth range | 2–55 m |
| When to see it | Year-round |
| Active | Day |
| Conservation status | Least Concern |
How To Identify It
The front half is black or dark brown, the rear white to pale yellow, with the division usually sharp. Colour proportions vary between individuals and with mood.
Where You Will See It In Cozumel
On every reef, on coral heads and rubble at all recreational depths. Among the most abundant fish on the island.
Reliable sites: Paradise Reef, Chankanaab, Yucab, Tormentos, Paso del Cedral.
Behaviour
Territorial. Each fish holds a small area of reef, farms algae on it, and drives off intruders many times its size — including parrotfish, and occasionally a diver's fingers or camera dome.
Males guard nests of eggs laid on cleared hard surfaces and become noticeably more aggressive while doing so.
Commonly Confused With
- Threespot damselfish — Adults have a dark spot at the tail base and on the dorsal fin.
- Cocoa damselfish — Yellow lower body and a blue-edged dark region.
- Dusky damselfish — Uniformly dark, without the sharp two-tone split.
Diving Etiquette And Safety
Keep fins off the reef and hands to yourself. Nothing here needs to be touched, moved or provoked to be seen well.
Part of the Cozumel marine life guide · see Cozumel dive sites · plan your Cozumel dive trip
Photo © Stephen Hoerler, courtesy of the Cozumel Coral Reef Restoration Program, used with permission.
Bicolor Damselfish Photos