50 per cent of fresh fish sold in supermarkets comes from farms

One obvious response to the disappearance of wild fish from our seas is "Why don’t we replace them with farmed varieties. We do it with land animals, so why not fish?" Of course this is already happening – over 40 per cent of the world's fish production already comes from aquaculture, and 50 per cent of fish sold in UK supermarkets comes from farms. These pen-reared fish grow at a phenomenal rate. For example, wild cod double in size every year, but hatchery cod quadruple in the same period. Given that size determines reproductive rate, at first glance this could be a solution to repopulating wild stocks.