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Sea of Cortez 810

Family Pomacentridae
Class: Actinopterygii (ray-finned)
Order: Perciformes

Key Features:
Deep bodied with laterally compressed body.  Typically small reef residents.  Very common in many environments.  Most are sequential hermaphrodites and are highly territorial demersal spawners.  Often exhibit dramatic morphological and coloration shifts between juveniles and adults.   


Notable Species in the Sea of Cortez

Abudefduf troschelii
Panamic Sergeant Major
Stegastes rectifraenum
Cortez Damselfish
Stegastes flavilatus
Beaubrummel Damselfish
Microspathodon dorsalis
Giant Damselfish
Chromis atrilobata
Scissortail Damselfish
Chromis limbaughi
Bicolored Chromis

Abudefduf troschelii, panamic sergeant major photographed in puerto penascu, Sonora Mexico

Abudefduf troschelii
Panamic Sergeant Major

Puerto Penasco, Sonora, Mexico

Family Pomacentridae
Damselfishes (Castanuelas)

Closely related to freshwater cichlids, the damselfishes are common residents of reefs throughout the world’s oceans.  The best-known members of this family are the clownfishes, but no clownfish are found in the Sea of Cortez, likely due to the absence of a suitable host anemone species with whom clownfish form intimate relationships.  

Damselfishes within the Gulf are often solitary, or school in poorly organized aggregations.  Only scissortail damsels Chromis atrilobata typically exhibit a well-defined schooling behavior, often associating with Cortez angels, Holocanthus passer at offshore islands.

Most damsels are demersal spawners that deposit clusters of eggs on rocky substrates.  Highly territorial, damselfishes will fearlessly defend their nests.  Scuba divers that do not pay attention to where they are moving their hands may be surprised to find a tiny, two-inch Cortez damselfish, Stegastes rectifraenum biting their hand and attempting to push the diver out of its territory.  While the bite is not painful, the ferocity of this diminutive fish is startling to say the least!

One of the most common and visually appealing of the Gulf damselfishes is the Panamic Sergeant Major Abudefduf troschelii.  Scuba divers and snorlelers should keep their eyes out for nesting males throughout the spring and summer.  Males will take on a deep indigo coloration to attract females to their nest sites, which may contain over six thousand eggs.  Spawning occurs every two weeks, until early fall. Found throughout the Gulf, juveniles can even be found in the tidepools of Puerto Penasco, and adults can be found scuba diving at depths from a few inches to over 100 feet, although they are most common at depths shallower than 60 feet / 18 m.

The largest of the Gulf damsels is the giant damselfish, Microspathodon dorsalis, which reaches a length of up to 12in. (305 mm).  While mainly herbivorous, this in no way diminishes the aggressive nature of the fish as compared to its smaller omnivorous relatives.  Known to attempt to bully both divers and sea lions that intrude into its territory, it is a damselfish to be reckoned with.  Courtship and spawning behaviors occur in rocky reefs in shallow sub-tidal areas.    



Updated August 28, 2009

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