Jill, I got this one!
The answer to this question relates to how various tank strains of species are discovered in the first place. We get EBJDs in our tanks because we are breeding together two fish both known to carry the recessive trait for electric-blue colouration. You only get EBJDs if you have BGJDs or EBJDs to start with. The blue trait has been preserved by first finding a blue fish, then out-crossing this fish to wild-type JDs to produce carriers of this blue gene, BGJDs. In order to produce an EBJD from regular wild-type parents, a genetic mutation has to occur. This mutation will occur only randomly and in very few (perhaps only one) fry in a given spawn of hundreds, if at all. Finding this mutation can be likened to finding a needle in a haystack -- the odds are not in your favour at all. However, the mutation was found and preserved by some hobbyists in the 80s, so we now have EBJDs. Breeders today -- if they are even looking for EBJDs in their JD spawns -- may not be so fortunate.
To put this another way, expecting EBJDs to come out of two wild-type JD parents is the same as expecting two wild-type/black/striped convicts to produce pink/leucistic convicts, two green severa to produce gold or red spot fry, two silver angelfish to produce blushing, brown bristlenose plecos to produce albino, etc., etc. Without first breeding certain traits into a line, the chances of those traits just magically popping into existence are pretty remote. As an exercise, look at various wild-caught species that are for sale and see how many of them are the same as the crazy colour morphs you can get from tank-raised stock. Almost none, I'd wager. We have all these aquarium strains of fish because random genetic accidents were preserved by breeders; they are not typical for the wild-caught versions of these species. Now, some of these variants may actually occur in the wild, if the strain is strong enough, but with EBJDs especially, you don't get a strain established in the wild because any random EBJD that is produced would be lunch long before it grew to sexual maturity. It's not like there are secret colonies of EBJDs hiding in the lakes or anything.
Hope that helps clarify!
