Well we've had disastrous overfishing even with the common fisheries policy. There is no reason why the UK couldn't regulate its own fish stocks sustainably just as well as, if not better than the EU. In a way, this is beside the point. Yes I know that fish swim around and that spawning grounds don't respect territories. But geology and climate, on the whole, don't respect territories much either. We don't share our land-based natural resources cost-free with other countries. I see the fish in our territorial waters in the same way. And so does the overwhelming majority of our fishing industry. Those fish are ours.