It's humanity in a nutshell find something good, abuse it to the point where it is no longer useful, and then complain that they've run out and no-one will do anything to help them, when it was their responsibility.
I'm not a vast fan of fish anyway, I eat occasionally, but very rarely, but with the supplies of North Sea Cod dropping to frightening levels, an with Tuna, Mackeral and Salmon all headed in the same direction through over-fishing, yes, we need to learn moderation, fish is a vital food supply, we cannot simply stop, but we do need to get some hard and fast international laws in place. Then, of course, you have to worry about the livelihoods of Fishermen who get paid by how much they catch.
The big danger is that countries are very funny about 'international waters' and 'territorial waters', the borders on land are pretty hard and fast, but there have very nearly been wars over where a countries influence extends into the ocean (UK and Iceland nearly came to blows about that a good few years ago). That's why these rules need to be international, and apply to every ocean, but the chances are that Nordic countries, which rely heavily on the income, and Japan, who, despite being the most modern country in the world, still go and hunt whales for fat which is no longer needed, would simply boycott such a rule, and there's limited powers to enforce them.
Edit: The thing is, 60 years ago, a fisherman used old equipment and was trying to earn enough to keep the house and feed the family, nowadays, he/she is using Mass-Trawling devices and the objective is to line the pockets of a corporation, which is a far hungrier beast.
