Once you stock the pond you can fish that fish indefinitely so I don't see any reason to stock the pond again with the same fish. That'd just be a waste. What -could- happen (I have never tested it ( is that you get another spot in the pond for the same fish but that'd be a waste of a spot when you could use other fish instead.
Max: "I think he just needs a hug, or a sharp blow to the head." Yes, I -am- a girl gamer.