Opistognathus rosenblatti

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Common Name/s: Blue-spotted Jawfish
Maximum Adult Size: 10cm
Natural Distribution: Eastern Central Pacific: Gulf of California
Depth Range: ? – 12 m
Species Notes & Captive Care Notes: Once rare in the trade and expensive, the Bluespotted Jawfish has recently seen a surge in availability to UK hobbyists and as such, prices have fallen considerably. O. rosenblatti is found in the Gulf of California, usually favouring flat areas around the base of submarine cliff-faces. Like O. aurifrons, they reach about 10cm in length on average. The mating ritual of this species begins with the posterior half of the male fish turning white. Repeatedly darting in and out of its den, this results in conspicuous flashes of white which perhaps serve to entice the females. Outside of the spawning season, the background colour of the fish is an orange-brown to yellow and this is overlaid with stunning neon blue spots. It is worth noting that a reasonably large aquarium is advisable with this species, and even more so if a pair is planned as it can be rather more aggressive than O. aurifrons. In the wild, dens can be up to 1 – 3 metres apart. Here, bluespotted jawfishes spend their days hovering a few inches above burrows constructed from pieces of dead coral skeleton, shells and rubble. Individual dens are usually separated by at least one metre, and colonies sometimes number hundreds of individuals. With a 360 degree view of their surroundings, they pluck zooplankton from the currents, darting back into their burrow if danger threatens. They also spend time maintaining their dens, fastidiously rearranging them to ensure they are secure. This includes covering their burrow entrance at dusk and then uncovering it each morning. Males become bright white in the front half of their bodies during spawning and courtship. Perhaps the primary concern for housing such a fish in captivity is providing the right kind of substrate. A minimum of 9cm depth is required (based on observations of minimum burrow depth in the wild). To allow effective construction, a good mix of substrates should be provided, including mixed grade gravel plus shells, rubble and even dead coral branches. Extra materials should be added occasionally indeed this can limit disruption to other areas of the sand bed. Growing to approx. 12cm)in length, a 150 litre aquarium should be considered the very minimum for a single specimen. Housing more than one would require a very large tank (see territory size notes above). The tank-mates chosen also have major behavioural and health implications. Large fast-moving fishes, even non predatory species will keep the fish from leaving its burrow and it may not be able to feed sufficiently. A specimen added into such a mix is unlikely to settle and therefore will be prone to jumping from an aquarium if no cover is fitted. A better option would be to add the jawfish early and allow it to settle before other fishes are added. A jawfish that hides under rockwork or fails to leave its burrow completely is demonstrating unnatural behaviour indicative of stress. Providing the fish feels comfortable enough to leave it’s burrow and is not outcompeted by more aggressive feeders, it’s diet should consist of a variety of floating meaty foods fed at least three times per day. Using a turkey baster to get the food near to the burrow can help during the settling period. It is worth noting that this species has been known to stop feeding for several days on introduction to a new system but given the right conditions they are usually hardy and disease resistant. Starvation or escape from the tank is the most likely problem. Opistognathus panamaensis is a similar species but the spots gradually fuse into stripes towards the tail

References / Further Reading:
IUCN page with zoomable range map

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