maybee there not hybrids? just mutants? and some males are fertile just a high percent are not, but when you have a pond full of them, chances are you will have a couple fertile males, and thats how they breed them overseas.
i dont kow where they came from or how they got there, ut i dont believe they are born steril. i was informed by a reliable scource that most hybrids that are bred by responsible breeders are passed through a tube that is saturated with UV light and the UV rays are so powerful that it mutates the reproductive systems. i say responsible breeders because if these fish were not sterilized they will end up in the wild and it also keeps the profit in the breeders favor...