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Fish Absolutely: Electric Blue Jack Dempsey


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One of the oldest cichlids in the trade, the Jack Dempsey (Rocio octofasciata) got its name from the famous 1920s boxer, who like this fish was known for his aggressive nature and striking features. Within the past 10 years though, another variation of this fish has emerged, the electric blue Jack Dempsey (EBJ).

The original variety, which was collected from the wild, came from Central America and was quickly bred by aquaculturists worldwide. The blue version has not been documented to occur naturally in the wild. There is great debate as to whether this fish has been hybridized or genetically altered through selective breeding. Some argue the fact that this fish is simply a viable Jack Dempsey (R. octofasciata).

With the exception of color, the EBJ does have similar exterior characteristics as the original variety. But unlike their wild cousins, EBJs do not grow as quickly, or to the same maximum size. It has been observed that they are also not as territorial, or as predatory, as the natural specimens. With a higher juvenile death rate, there is no doubt EBJs are more prone to diseases than their natural cousins.

So is it natural or not?

I’ve read reports where hobbyists claim DNA studies have resulted in EBJs being proven a “real Dempsey.” But I’ve also heard reports that indicate that such DNA studies are inconclusive. To date, there does not seem to be any scientifically reviewed study on the subject. Quite a few ichthyologists in South America are skeptical about their natural genomes. Upon observation, one might notice certain anatomical variances in the buccal cavity, cranial shape and dorso-ventral measurements. Although, keep in mind this does not prove anything definitively. Original breeders and exporters of EBJs explain that the blue gene is recessive, which is why we would never see them in the wild. It is a mutated gene, and the recessive inheritance is brought out through multiple generations. This may explain why the fish is “runt-ish” when compared to natural Dempseys. It also would explain their slower growth, low juvenile survival rate and weakened immune response.  Many believe something was done to create this fish. The use of hormones to induce spawning or hybridization, or possibly non-natural egg/larvae rearing, has been speculated. Breeders of the first EBJs have not disclosed enough to information to make a determination based on reasonable data.

“Frankenstein-ed” or natural, the electric blue Jack Dempsey is new to us, and their popularity is growing, as is their demand. Like parrot fish, flowerhorns and Glo-Fish, they are finding their way into home aquariums around the world. I hope we will get a bonafide scientific study on the DNA of these fish, so we will know what we are really selling.

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