Overfishing has significantly reduced the populations of larger species of marine fish. In fact, stocks of large fish have declined by two-thirds in one century. These findings come from an international research team who carefully analysed more than 200 ocean ecosystem models across the globe, to assess the evolution of the world fish biomass from 1880 to 2007. The scientists highlighted a collapse in stocks of tuna, grouper, sharks and other top predators, with a chain reaction on a global scale, affecting the food webs and ecosystem equilibrium.