Is the end of sushi upon us? It may well be. Bluefin tuna stocks all over the world are on the verge of collapse, thanks to overfishing. The World Wildlife Federation has estimated that Northern bluefin could get wiped out within three years, while the Southern bluefin is critically endangered. If those two species vanish, fisherman will set their sights on the only-slightly-less-beleaguered Pacific bluefin, which, presumably, won't appreciate the newfound attention.