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Sea of Cortez 810

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

Key Features:
Known for bright colors and dramatic color patterns, the butterflyfishes are closely related to another splendor of the reef, the angelfishes.  Butterflyfishes may be differentiated from angelfishes in that butterflyfishes lack the prominent pre-opercular spine found in the angelfishes.  Butterflyfishes are typically very deep-bodied, and strongly laterally compressed.  Butterflyfishes have a continuous dorsal fin and a rounded or truncate caudal fin.     


Notable Species in the Sea of Cortez

Chaetodon humeralis
Threebanded Butterflyfish
Johnrandallia nigrirostris
Chaetodon falcifer
Scythe Butterflyfish
Forcipiger flavissimus
Longnose Butterflyfish

Johnrandallia nigrirostris barberfish Guaymas, Sonora, Mexico in Sea of Cortez

Johnrandallia nigrirostris

Guaymas, Sonora, Mexico

Family Chaetodontidae
Butterflyfishes (mariposas)

Closely related to the angelfishes, (family Pomacanthidae), identification of butterflyfishes may be most easily accomplished by noting the lack of the strong pre-opercular spine that is present in angelfishes.  In addition, unlike the angelfishes, butterflyfishes do not undergo a striking change in color and pattern as they mature. 

The term Chaetodontidae literally translates to bristle tooth. The small brush-like teeth within this family are well adapted to the picking and cleaning feeding behaviors that are employed by many members of this family.  Limited by their comparatively small mouths, the butterflyfish often establish feeding stations where they work in small groups to clean parasites off of larger fishes, many of which would otherwise make a snack out of reef fishes this size. 

The Sea of Cortez contains four species of butterflyfishes within three genera.  The commonest butterflyfish in the Sea of Cortez as well as the tropical eastern Pacific is the threebanded butterflyfish, Chaetodon humeralis.  This social butterflyfish is found either in pairs or in small to moderate sized groups.  Found more commonly along the mainland side of the Gulf, it is most often encountered by scuba divers from Bahia Kino and Guaymas south to Peru.  These butterflyfishes generally prefer relatively shallow depths of less than sixty feet although they have occasionally been encountered at depths of up to two hundred feet, where they have been observed picking amphipods off of black coral colonies. 

The best known of the cleaning fishes in the Sea of Cortez is the barberfish, Johnrandallia nigrirostris.  Similar in habitat and depth range to the three-banded butterflyfish it is differentiated by its color pattern.  A strong black mask extends over the face and eye.  A second black band covers the dorsal crest somewhat above the lateral line.  There is no coloration between the first and fourth dorsal spines.  This discontinuous coloration differentiates it from the scythe butterflyfish and the lack of multiple bands differentiates it from the threebanded butterflyfish. 

The aforementioned scythe butterflyfish, Chaetodon falcifer, is the only deep-water species of butterflyfish found in the Sea of Cortez.  It is mainly found in the southern Gulf and is especially prevalent from Cabo San Lucas and Isla Guadalupe south to the Galapagos Islands.  It is rarely observed in depths shallower than one hundred and fifty feet and has been reported from depths exceeding five hundred feet. 

The fourth species of butterflyfish in the Gulf is also mainly found in the Cape region, although it has been observed at Isla San Pedro Nolasco off of the coast of San Carlos.  The longnose butterflyfish, Forcipiger flavissimus, is identified by the lack of any black stripes on the rear of its body except for the black ocellus on the anal fin.  The combination of a bright yellow body and a deep black mask makes it a striking fish, difficult to confuse with any other Sea of Cortez butterflyfish. 



Updated August 28, 2009

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