Most of the food we eat - beef chicken, wheat, apples, corn - is farmed on the land, produced under controlled conditions and transported to market rather than gathered from its natural habitat. But one source of the world’s protein is still taken straight from the wild. Fish and other sea food. That's now changing, but should it? This week The Food Chain has a special programme about the ocean, and the meals we take from it. Tanya Beckett reports from Lisbon where world leaders are meeting to discuss the oceans' economic fate, while Audrey Tinline is in Norway asking whether fish can ever be a truly sustainable source of food.