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Family Opistognathidae
Jawfishes
Class: Actinopterygii (ray-finned)
Order: Perciformes

Key Features:
Jawfishes are a family of mainly small and secretive burrowing-fishes that resemble blennies.  They possess a single elongated dorsal fin that runs nearly the entire length of their bodies, from behind the operculum to the end of the caudal peduncle.  Their head is comparatively large, as are their eyes and mouth.  Males are mouthbrooders, and following copulation, the male will scoop up the fertilized eggs into his cavernous mouth, and brood them until hatch.      

Notable Species in the Sea of Cortez

Opistognathus rosenblatti
Bluespotted Jawfish
Opistognathus punctatus
Finespotted Jawfish
Opistognathus rhomaleus
Giant Jawfish
Opistognathus mexicanus
Mexican Jawfish
 

Bluespotted Jawfish Opistognathus rosenblattii, Isla San Pedro Martir, Sea of Cortez, Mexico

Opistognathus rosenblatti
Bluespotted Jawfish

Isla San Pedro Martir, Mexico

 

Family Opistognathidae
Jawfishes (Bocas grandes)


Generally resembling gobies and blennies, the jawfishes are a widely distributed group of burrowing fishes.  There are at least ninety species of jawfishes worldwide but little is known about many members of this secretive group and approximately one third of the species remain undescribed. 

Most species of jawfishes prefer to live in sandy bottoms or fields of coralline algae rubble where they construct deep and often complex burrows.  They never seem satisfied with their work and jawfishes may be observed throughout the day spitting out rocks and sand that they have cleaned from their burrows and seem to constantly rearrange the rocks and other landscaping surrounding their borrows.  Identification of the various species may be difficult given that often, only the face is available for study for a scuba diver peering down into a burrow.     

Within the Sea of Cortez there are at least eight species of jawfishes.  However, relatively few species are observed with any frequency by scuba divers.   Although the majority of jawfishes in the Gulf are six inches or fewer in length, there are several species that can reach nearly two feet in length. 

One of the most interesting aspects of this group of fishes is their elaborate courtship and reproductive strategies.  Males will court females by darting above their burrow and hanging motionless in mid-water with their dorsal and pelvic fins extended.  After a few seconds males will dive back into their burrows and will continue to repeat this dance for hours on end.  Females must leave the relative safety of their burrows, to join a male in his burrow in order to reproduce.  Thus, the females are highly selective with regards to the quality of the courtship display.  Similar to the cardinal fishes, following spawning the male jawfish will mouth-brood the clutch of eggs until they hatch. 

In contrast to most of the drably colored and well-camouflaged Sea of Cortez jawfishes, such as the fine-spotted jawfish Opistognathus punctatus, the blue spotted jawfish, Opistognathus rosenblatti, is exquisitely colored.  Against a body of beige and yellow, iridescent blue spots draw dramatic attention to this fish.  During courtship displays however, the males are barely recognizable as being from the same species.  During these displays the posterior region of the fish will become nearly black, with the anterior a very light yellow to white.  The pelvic and caudal fins are a light yellow.  During spawning season, dozens of these males will begin flashing over a small patch of sand where they live in loosely organized colonies.  The blue spotted jawfish is found most often in offshore islands in Sonora and Baja and seems to be particularly abundant at Isla San Pedro Martir.

 

Updated August 28, 2009

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