Are the oceans big enough to keep up with Chinese demand? And is fish farming the answer? Presenter Laurence Knight visits Shanghai's gigantic fish market, where seafood importer Peng Song explains why the rise of the Chinese middle class is being felt everywhere from Canadian lobster farms to British fish and chips shops. Meanwhile Joshua Thorpe reports from The Gambia, where local fishermen bemoan the illegal incursions of big foreign trawlers. Plus Manuel Barange of the UN's Food and Agriculture Organization. (Picture: Crab on sale in the Shanghai fish market; Credit: BBC)