That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.  In the jawfishes (Family Opistognathidae) we find some of the most entertaining and interesting of all marine aquarium subjects.  Constantly popping in and out of their uniquely constructed burrows, all are very active and quite comical to behold.  Although perpetually occupied with minor territorial disputes, they get along well in groups, and are quite willing to display a wide range of interesting behaviors once they settle in.

Diversity and Lifestyle

Over 60 species of jawfishes, all inhabiting marine waters, may be found in the Indian Ocean, Western and Central Atlantic Ocean and the Pacific Ocean (from the Gulf of California to Panama).  

Jawfishes sport huge eyes and mouths on an enlarged, blunt head that, to many, evokes the image of a bulldog.  The body tapers quickly behind this, suiting them well to the burrowing lifestyle that all have adopted.  The strong jaws and head are used to hollow out subterranean retreats, while the slender body allows the fish to quickly slip inside, tail-first, at the slightest sign of danger. 

Jawfishes rarely stray far from home, making short feeding or defensive forays but generally staying within easy reach of the burrow’s entrance.  Most cover the entrance of their homes with a pebble at night, and the males of all species incubate the eggs within their mouths.

Yellow-Headed Jawfish (Opistognathus aurifrons)

A group of these beautiful fishes in established burrows makes a delightful exhibit, with bright yellow heads constantly appearing and disappearing as they survey their territories for food or foes.  They slip tail-first into their homes with amazing speed, and pop out just as quickly.  Growing to a length of 5 inches, the body of the yellow-headed jawfish is delicately colored in pale blue. 

 

In contrast to many other fishes that maintain a regular home base, yellow-headed (and most other) jawfishes are relatively inoffensive towards one another.

Providing the Right Substrate

Jawfishes require a substrate that allows for the creation of burrows that retain their structure and can serve as permanent homes.  Without such, they will fare poorly.  You may need to do a bit of experimenting, in terms of substrate composition, if you add jawfishes to an established aquarium. 

If you are starting from scratch, a 1:1 mix of our Natural Ocean Substrate  and Pearl Beach Aragonite will work well.

Diet

Jawfishes readily feed on all manner of animal based frozen and pelleted  foods, and particularly relish live brine shrimp, Mysids and blackworms.

They are quite alert and vigorous feeders, but please be aware that many individuals will not venture far from their burrow.  Therefore, be sure that a suitable amount of food is placed within easy reach, lest they be out-competed by less “homebound” species.

A Caution

Jawfishes scuttle about but rarely swim, and so we tend to think of them as “bottom fish”.  However, for reasons as yet unexplained, they frequently manage to jump out of aquariums at night. 

I’ve not had the opportunity to watch jawfishes with the assistance of a night-viewing bulb, so as to perhaps understand just what it is they do after dark…please write in if you beat me to it.  In the meantime, be sure that your aquarium hood fits securely, especially around filter tubes and other equipment.

Further Reading

The Monterey Bay Aquarium exhibits yellow headed jawfishes, and has posted interesting information here.

Please write in with your questions and comments.  Thanks, until next time, Frank Indiviglio.