Thanks to our insatiable appetite for sushi, the global supply of bluefin tuna has been depleted by as much as 80 percent since the 1950s. The bluefin is an apex predator, so when it’s gone, the fish it eats will decimate the species they eat until the oceans are empty of everything but invertebrates. This perilous situation provides the unifying thread for this 2011 documentary, which wanders from sushi’s origins as an occasional meal to its ignoble status as a convenience food that threatens aquatic life. Unlike the recent Jiro Dreams of Sushi, it doesn’t inspire conflicting feelings of guilt and hunger—it’s nearly devoid of fish fetishism (the makimono served in a Polish restaurant looks downright manky). Director Mark Hall also ends on a hopeful note, profiling restaurateurs that serve only sustainable species and an Australian tycoon who may have figured out how to breed bluefin in captivity.