Huge ships now trawl the seas, catching fish such as tuna in bulk, and leaving little for local fishermen in their much smaller boats.
David O’Shea reports from the southern Indian Ocean and boards a Greenpeace vessel to find out more about the multi-million dollar international trade. Out in the middle of the ocean, he finds the lines are blurred over legal and illegal catches, with no way of tracking the fish passed between ships registered in several different countries.
So, what’s really going on out of sight on the high seas?