There are certain reef fish that have loads of good looks, plus plenty of personality. The bluespotted jawfish (Opistognathus rosenblatti) is one such fish. While it is only sporadically available and commands a higher price than some of its less colorful kin, the bluespotted jawfish is worth seeking out and acquiring for your community aquarium.
Difficulty: The bluespotted jawfish is a durable aquarium fish. The biggest cause of death in this species is suicide. This species will frequently leap from “topless” aquariums and end up as fish “jerky.” Don’t be too sure that you’ll keep your bluespotted jawfish in the aquarium if the top is not fully covered — it has the uncanny ability to find insignificant apertures in the top back strip through which to leap! Other than its hara-kiri tendencies, the bluespotted jawfish is a relatively easy fish to keep. Feed it well with frozen foods, such as mysid shrimp, frozen preparations for carnivores and frozen seafood shavings. Feed the bluespotted jawfish at least once a day, preferably a couple of times a day.
Physical description: The bluespotted jawfish is reddish brown overall with bright blue spots all over the head and body. When male bluespotted jawfish display to mates during the spawning period, the front of the body turns pale and the rear portion of the body turns black. The bluespotted jawfish reaches a length of 4 inches.
Range: The bluespotted jawfish is one of a handful of fish collected from the Gulf of California. The bluespotted jawfish tends to occur at depth of 60 feet or deeper on slopes consisting of sand with mixed shell and pebbles. The bluespotted jawfish lives in groups, but there is usually greater inter-individual distance between colony members than some other grouping jawfish (e.g., yellowhead jawfish, Opistognathus aurifrons). (The bluespotted jawfish are usually from 3 to 10 feet apart, while the distance of nearest neighbors in the yellowhead jawfish is usually 1 to 4 feet). The bluespotted jawfish is a zooplankton-feeder that will hover in the water column just above its burrow and eat passing planktors.
Compatibility: The bluespotted jawfish is a relatively docile aquarium inhabitant. The bluespotted jawfish normally ignores its neighbors unless they attempt to invade its burrow. In that case, it will try to evict the gate-crasher. The bluespotted jawfish will also display at fish that get too close to the entrance of their home. The display consists of expanding both the jaws and gill covers, while it simultaneously charges toward the intruder. Other burrow-dwellers, such as shrimpgobies, dartfish and wormfish are most likely to raise the bluespotted jawfish’s ire. While bluespotted jawfish often occur in colonies in the wild, they are not tolerant of each other in the aquarium. On the other hand, the pistol shrimp (Alpheus spp.) that live in association with shrimpgobies may evict a bluespotted jawfish from its burrow. You can keep a pair of Opistognathus rosenblatti, but no sexual differences in color are known (except the temporary change that occurs during courtship described above). Bluespotted jawfish pairing will require adding a pair of fish together and watching to see what happens. If they fight, remove one bluespotted jawfish and try another individual. The bluespotted jawfish is great for the reef aquarium, but it may spit the sand on corals that are near the burrow entrance.
Aquarium conditions: The bluespotted jawfish aquarium must have sand bed at least 4 inches (and preferably 6 inches) deep. The substrate should not consist of a uniform grain size, but instead should include bits of coral rubble, shells and crushed coral along with the sand. This material will allow the bluespotted jawfish to create more stable burrows. Acceptable water parameters for the bluespotted jawfish are: pH of 8.1 to 8.4, specific gravity of 1.019 to 1.025 and a water temperature of 72 to 82 degrees Fahrenheit.
Care considerations: Successful long-term care of the bluespotted jawfish comes down to a covered aquarium, good tankmate selection (stay away from bellicose neighbors, at least until it has acclimated to its home aquarium) and a moderate to deep sand bed.
Breeding: The bluespotted jawfish orally incubates its eggs. The male bluespotted jawfish takes them into its oversized mouth and holds them until they hatch. At this time, he spits out the larvae, and they begin a planktonic lifestyle.