Every year, scientists are employed to give guidance to the EU on the maximum catch for the year. This in turn is then usually doubled or tripled by the EU. Add to that the illegal catches, and the total catch is probably a quadruple of the amount deemed sustainable by science. This has been going on for many years, and we are reaping the rewards.
If the scientific guidance was adhered to, there would sadly be massive job losses in the fishing industry and reliant industries, probably causing severe political outfall and loss of said politicians jobs. As we all know, politicians don't like giving up power, and so this situation will continue until fishing ceases to be commercially viable, or we vote people in who are less selfish.
I think that a much larger area of the worlds oceans should be set aside as marine conservation areas. We would all have to pay much more for our sea fish, and probably start eating other species but its better than having no fish left in the sea.
Anyone fancy some deep fried jellyfish or some crispy aromatic sea cucumber? mmmmn, tasty...