If fish are being bred to accomplish survival in the wild, I couldn’t agree more — major threat to ecology to move tank-exposed fish back out into existing populations, what with the potential foreign diseases they’ve been exposed to, the existing social structures and territories they’d be tossed into, the social cues and behavioral interactions they missed out on growing up in the bizarre environment of a tank, and a host of other good reasons. This holds true whether the body plan has changed through the generations or not. On the other hand, I rather like the fancy guppies in my tanks, which bear little resemblance to their wild genetic forebears that they’ll never have to survive alongside.
Just to clarify, though, I’m personally very interested in maintaining my breeding lines as close as possible to the wild populations. This is why I was interested in earlier threads in hearing how much variation people had noted in their wild-caught fish, in hearing if anyone had experience maintaining carefully documented outbreeding programs, and my interest in swapping stock with others to keep the diversity as high as possible. I’m excited that there are so many of us working together and able to swap so we can keep the bloodlines as “true” as possible.