Ask the WWM Crew
|Please visit our Sponsors|
Back in the early days of the marine aquarium hobby (the 1950s) there was a very limited choice in saltwater livestock. Hard to believe now, but there were nary any reef keepers; in fact, the number of invertebrates offered for sale could be counted on two hands. Fish selection wasnt much better, with most offerings coming out of the tropical West Atlantic These counted some Hamlets (genus Hypoplectrus), Royal Grammas (Gramma loreto) and the occasional wrasse, angel, butterfly and damsel. The Pearly Jawfish should be proudly included in this stalwart collection; presenting many good aquarium-suitable traits. This species is relatively easy to collect, holds and ships well, adapts well to captive conditions and importantly beyond, its good-looking and very interesting behaviorally.
Stock requirements of keeping this species are the provision of adequate bottom/floor space (1-2 square per specimen, made up of mixed rubble and soft sand to allow permanent tunneling; oh, and a good complete top to prevent their launching themselves out of their system.
Jawfishes possess cylindrical, oblong body shapes, long continuous dorsal and anal fins and way-too big mouths ("Opisto" = behind, "gnath" = mouth, is in reference to their receding jaws). These characteristics and their enormous, all-seeing eyes make them unmistakable.
Some other more defining, distinguishing characteristics are their bodies being covered with cycloid scales, though their heads are "naked" of scales, spines and other processes. This feature aiding them in their continuous burrowing.
The one trait that separates the opistognathids from all other perciform (Order Perciformes, the largest order of fishes) is the arrangement of fin supports in their pelvics. These have one spine and five soft rays (inner three weak and branched and the outer two stout and unbranched).
Opistognathids are all marine; western
and central Atlantic, Indian and both coasts of the Pacific. There are
three genera (Opistognathus, Lonchopishtus, Stalix) with about
sixty described species with several others under study. Most are less
than ten centimeters, though a notable few attain half a meter in total
The Pearly Jaw spends ninety nine or so percent of the time either all the way in its burrow or with just part of its head exposed. Though they can become quite tame with time, the right, very peaceful settings, and stocking with their own kind, most individuals continue to be secretive to the utmost. About the only time one generally sees a Jaw all the way exposed is either during feeding sessions or territorial displays. In fact, it is not uncommon for Jawfishes to do as symbiotic Pistol Shrimp and Goby combinations do, and close off the openings to their burrows at night and even during daytimes if they dont want to be disturbed.
If your Jaws go MIA for days, dont overreact and imagine the worst;
definitely dont start taking the tank apart. Jawfishes can easily go a
week to ten days w/o feeding. More times than not theyre still there,
hiding, doing whatever it is fish do when they want to remain out of
the limelight. And if indeed the worst has occurred, their mass is
small enough that scavengers and decomposers will clean up the remains
Ideally these fish/es are better to best presented in a species-only setting; that is, with a few of their own species as principal, central exhibits. If they are to be mixed with other organisms, other than sedentary ones like corals, these tankmates should be non-aggressive (No triggers, eels, large basses or wrasses), at least not predatory on small fishes and few in number. Too often, one finds that Jawfishes are lost due to stress and undernourishment from being placed in too active, too crowded settings. Give yours room and peace.
The Pearly Jawfish is about as reef safe as marine fishes can be not chewing on stinging-celled life, leaving clams, shrimp of any size, and all other fishes alone.
Good tankmates are slow moving fishes like Cardinals, and medium to upper water column choices such as Fancy Basses (Anthiines) and Fairy Wrasses (Cirrhilabrus species). Another great gauge to use is to seek out the types of life found in these fishs tropical West Atlantic setting and mimic (make a biotope) of this setting, including choices of livestock. Gramma loreto are found in rocky outcroppings near the sand flats where O. aurifrons calls home, as are TWA Butterflyfishes, Hamlets (genus Hypoplectrus), indigenous Damselfishes and much more. Look about; youll find quite a few macro-algae species, sponges, gorgonians and more from this part of the world that are regularly offered in the trade.
The general rules of marine fish choosing apply to Jawfish picking: First and foremost look for well-fleshed and adjusted specimens. Emaciated individuals that are not burrowing are likely doomed.
If youre interested in breeding these fish, you will need to spend some time closely observing specimens as they interact. Jaws arent easily sexed by morphological or colour differences, and thus its best to let them do the sorting themselves. Otherwise, and especially if buying smaller, captive-produced individuals, you are encouraged to place five or six in a suitable setting and allow them to develop pairing.
System size is important with this species of Jawfish. Though for the family, Opistognathus aurifrons is highly social, do provide two square feet of uncrowded bottom space for the first individual, and one square foot to share for every additional. Having more than one specimen is highly recommended, though the species can do well solo, but with more you will experience MUCH more social interaction and have greatly more fun keeping them. Oh, and when you see them crowded together at stores/wholesalers, do remember/keep in mind that this is only meant to be a temporary situation. Not natural or sustainable.
Having a good depth (at least 3-4 inches) of a mixed grade of substrate, including some bivalve shells for covers, is requisite for keeping these fishs. They are prodigious burrowers and will be very unhappy and hence unhealthy if not given their media. The blending of finer sand with coarser rubble bits in at least one area allows the Jaw to reinforce its tunneling, and even if provided, you may find yours digging under rockwork which reminds me to mention that you want to assure your rock is setting directly on the bottom of your system to prevent toppling due to destabilization.
If you have a concern that your Jaw/s may burrow too much into your substrate, you can do what folks with many types of plenum-arrangements do, and lay in a cover of all-plastic screen door mesh with just some gravel over it in the areas youd not have them dig.
Being true reef fishes, Jaws require reef water quality and the filtration to accomplish this. Perhaps doubly so, as their digging around can lead to a good deal more detritus being raised into the water. Here once again Ill plug the use of a relatively-large sized refugium tied in with your system, to provide continuous feeding, as well as the best in conditions.
Ive mentioned this and the familys members penchant for Houdini-ism; do take care to make sure there are no Jawfish body size openings through the top, unscreened plumbing, overflows that will allow them egress. For fishes that seem to spend most all the time, near or under the sand, they can and do regularly jump out of aquarium systems.
Most settings call for using something in the way of a feeding tube, syringe or turkey baster to get food items to the general vicinity of your Jaw/s. Otherwise, unless there is a good deal of endogenous live food production (e.g. a large, healthy tied-in refugium), your Jawfish may go undernourished.
I am a huge fan of using vitamin and HUFA supplements on a punctuated (periodic, once, twice a week) basis, soaking foods to be proffered for a few to several minutes ahead of using. There are numerous reports of likely nutritional-related blindness in this species, and spontaneous cures brought about apparently from the use of such additives. I take vitamins myself and encourage you to do so and provide them for your aquatic livestock.
I put all Jawfishes in the category of better not to quarantine, along with most gobies, blennioids and others; for the sake of preventing too much stress and loss from same and starvation. Better by far to do a cursory pH-adjusted freshwater bath (five minutes or so) w/ or w/o Methylene Blue to knock off external parasites that can be thus dislodged, and place the specimen/s directly in the prepared main/display system.
Though less susceptible to the usual external parasite scourges than most marines, Jawfishes do contract them, and dont appreciate toxic treatments (metals, dyes, formalin). You are encouraged to move all fishes to a separate treatment tank and utilize the Quinine, Chloroquine Phosphate if youre keeping Opistognathids.
Opistognathus aurifrons has been cultured to maturity in aquariums, though most specimens are still wild-collected. They may be gathered or set up pairs for your acquisition. Most are encountered paired in the wild, with males doing a ritualistic dance to signal intentions to their mates. These consist of arched body approaches, with their fins erect at ninety degrees to their bodies. If successful females will spawn, males fertilize the eggs and pick them up in their mouths. Fertilized eggs are orally incubated for a week to ten days, mostly dependent upon water temperature. Commercial breeders move males with young to separate systems, to provide peace, and protection from predators. Incubating males are provided with pieces of PVC pipe for habitat.
The greatest and most common step/stumbling block occurs with providing sufficient food to the young once their small yolk sacs are absorbed in two-three days. Many early attempts involved Rotifers as initial foods, but likely small species of copepods (collected or purchased as stock cultures), followed by newly-hatched Brine Shrimp are best. Young are released, becoming surface/plankton and floating about for about two weeks. Following this dispersal period they metamorphose into bottom dwelling, very-small versions of the adult form, growing quickly under ideal conditions, digging into fine sand.
The Pearly Jawfish has been an integral part of the marine aquarium hobby from its origins in the 1950s. Though it has been commercially and privately spawned and reared in captivity, specimens are still mainly wild-collected. These prove to be very hardy shippers and adapters to captive conditions; demanding only a not-too-busy setting with some depth of mixed substrate to burrow and regular small animal feedings.
Baensch, Hans A. & Helmut Debelius. 1994. Marine Atlas, v. 1. MERGUS, Germany.
Chlupaty, Peter. 1978. The fish with the golden head. TFH 8/78.
Colin, Patrick L. 1972. Daily activity patterns and effects of environmental conditions on the behavior of the Yellowhead Jawfish Opistognathus aurifrons, with notes on its ecology. Zoologica 57(4):37-169.
Fenner, Robert. 1996. Jawfishes. TFH 8/96.
Fenner, Robert. 1998. The Conscientious Marine Aquarist. Microcosm, VT. 432pp.
Kerstitch, Alex. 1988. Master builders (re the family). SeaScope Winter 88.
Lobel, Phil S. 1982. The Yellowhead Jawfish; Opistognathus aurifrons. FAMA 4/82.
Lougher, Tristan. 2008. The Jawfish. Marine World, 4-5/08.
Marsden, Adrian. 2001. Doing what comes naturally. Yellow-headed Jawfish. TFH 4/01.
Michael, Scott. 2000. The whimsical Jawfishes. AFM 8/00.
Nelson, Joseph S. 1994. Fishes of the World, 3rd ed. John Wiley & Sons, Inc. NY.
Noyes, John C. 1974. Yellowhead Jawfish. Marine Aquarist 5(2):74.
Randall, John E. 1968. Caribbean Reef Fishes. TFH Publ.s, NJ.
Stratton, Richard F. 1993. The Yellowhead Jawfish. TFH 3/93.
Straughan, Robert P.L. 1965. The Pearly Jawfish, a sea nymph. TFH 1/65.
Young, Forrest A. 1982. The Yellowhead Jawfish; breeding the marine mouthbrooder in captivity. FAMA 4/82.