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Opistognathus rosenblatti - Blue-Spotted Jawfsih
The Aquarium Jawfish of Choice

The blue-spotted jawfish (Opistognathus rosenblatti) is a beautiful and behaviorally interesting fish that can make an excellent aquarium inhabitant if the aquarist focuses on some basic husbandry practices. This highly sought-after fish can average more than $25 an inch, so it’s worth knowing what environment will yield the highest chances of success. Most aquarists who keep a blue-spotted jawfish agree that this stunning fish is worth every penny.

Jawfishes in General

The blue-spotted jawfish is a member of the Family Opistognathidae. There are more than 60 described species in at least three genera. All jawfishes are sand-dwelling fishes, and most are quite small (the largest known jawfish reaches only about 51 centimeters). They all possess large mouths with which they dig burrows in sand, mud or reef rubble. Some species will share their burrows with other animals such as various species of shrimp from the genus Palaemonella or even wormfishes (microdesmids). All are elongate fishes and may be called eel-like. Most species have large eyes, and several are dimorphic. A few are also dichromatic.

While some jawfishes, like the blue-spotted jawfish, are quite colorful, most are drab in appearance. Many species choose habitats with low flow in relatively shallow water, although there are several known deepwater jawfishes. All inhabit the burrows they build and continually re-engineer their homes. While some jawfishes dart out to feed on motile invertebrates on the substrate near the entrance to their burrows, many (like the blue-spotted jawfish) are actually zooplanktivores and feed in the water column above their burrows.  

All jawfishes are paternal mouthbrooders, whereby the male jawfish incubates the eggs in its mouth. The incubation times vary, but it is usually around a week in length, after which time the male releases the hatching larva into the water column. In as little as two weeks (up to about a month), small, but fully formed jawfish will descend from the water column and begin constructing their own burrows in the substrate. Several species of jawfish (including the blue-spotted jawfish) exhibit flamboyant courtship rituals with impressive flashing behavior intended to secure a mate.

Blue-Spotted Jawfish Specifics

Ranging throughout the Eastern Central Pacific and Gulf of California (Sea of Cortez) in water as deep as 33 meters (around 100 feet), the blue-spotted jawfish is small (to 10 centimeters) and readily identifiable by way of its square head, continuous dorsal fin and unmistakable blue and yellow coloration. Like other jawfishes, the blue-spotted jawfish has an oversized jaw, which it uses to burrow in the substrate. In the wild, this fish lives in large colonies of up to several hundred individuals, each with its own burrow. It feeds on benthic and planktonic invertebrates by hovering vertically in the space above its burrow and picking zooplankton from the water column.

Male bluespotted jawfish are known for their stunning courtship rituals where they burst from their burrow, flash prominently and then dive back into the burrow. During these flashing episodes, the animal’s color will change to dark or black posteriorly and a faded yellow or white anteriorly. The behavior will continue until the male successfully attracts a mate, which will eventually swim to his burrow where the mating will occur.  

Blue-Spotted Jawfish Aquarium Husbandry

The husbandry considerations for a blue-spotted jawfish are not unlike those for other jawfish species, with one notable exception. Of the most common aquarium jawfish species, the blue-spotted is one of the more aggressive when it comes to conspecifics. Although the blue-spotted jawfish is often found in large colonies in the wild, the responsible aquarist will keep in mind that those burrows are often separated by a meter or more. As such, it is prudent to only keep one blue-spotted jawfish per aquarium, unless a mated paid can be obtained. An aquarium of 200 gallons or more would be necessary to realistically keep two members of the species that are not known to be a mated pair.

The blue-spotted jawfish aquarium should be a fish-only or reef tank with a substantial sandbed (at least three inches) complete with live rock rubble in which this fish can build a network of tunnels. While they will build a burrow in soft, sandy substrate, this species prefers (and should be provided with) reef rubble and shell fragments. Be sure that all live rock in the tank is solidly arranged on the aquarium bottom or on rock lifts (not the sandbed), as burrowing under live rock can result in catastrophic avalanches.

The blue-spotted jawfish, like virtually all jawfishes, will jump. As such, the appropriate aquarium will have a well-fitted top of eggcrate or some other material to prevent the fish from launching itself out of the water and onto the floor. In addition to having a tight-fitting lid, the conscientious aquarist will do everything in his or her power to remove the causes for jumping. Toward this end, it is best to make sure that at least some of the aquarium lights remain on during the acclimation period. This fish needs to search for a suitable burrow-site and then construct an adequate burrow before it will begin to settle down. Leaving some light on to assist in the initial burrow-finding and digging activities will go a long way to helping a new specimen acclimate to the aquarium.

Another major factor in why a blue-spotted jawfish may jump has to do with tankmates. As already noted, this is an aggressive jawfish species when it comes to conspecifics, but other aggressive fishes, even smaller ones (e.g., dottybacks), most likely will stress a blue-spotted jawfish. It is best to keep this species of jawfish with peaceful fishes to avoid unnecessary jumping behavior.

Like all jawfishes, the blue-spotted jawfish will appreciate areas in the aquarium where the water flow is less than turbulent. Chaotic, turbulent flow can make maintaining a burrow very difficult, and this will only lead to stress. The aquarium should be no smaller than twenty gallons, with open areas in which to burrow being the most important consideration. The blue-spotted jawfish is generally considered reef-compatible.

Blue-Spotted Jawfish Diet

The blue-spotted jawfish will come to accept most commercially prepared foods for carnivores. Because they can be timid feeders in the presence of larger or more aggressive feeders in a community tank, it is a good idea to broadcast food using a turkey-baster near their burrow and observe the animal feeding. Small chunks of meaty seafood will be appreciated, as well as vitamin-enriched frozen, flake and pellet foods.

 

   
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