The world has fished past the point of "peak tuna." 50 years ago, much of the Atlantic bluefin tuna that found its way into fishermen's nets was thrown back or used for cat food. But when the modern sushi craze took root in Japan -- and spread to sushi aficionados worldwide -- demand for tuna meat skyrocketed. Tuna populations have now dwindled. The tuna populations in the Gulf of Mexico & Mediterranean have shrunk to less than 10 percent & 15 percent, respectively, of their pre-fishing size.