They are hybrids between Devils Hole Pupfish C. diabolis and Ash Meadows Amargosa Pupfish C. nevadensis mionectes. Many decades ago some "refuges" were constructed to provide new populations of Devils Hole Pupfish and in one of them a few individuals of the other species somehow got mixed in and created a very fecund hybrid population [the pure populations in the other refuge(s) failed and died out after a while]. The hybrid fish have been used for experimenting with captive breeding techniques and so forth (because there are too few Devils Hole Pupfish to risk), and also for education purposes.
