Rich in omega-3 fatty acids, cheap, and widely available, salmon is often listed as an essential part of any diet. A delicious and versatile fish, it can be used to make sashimi, cold smoked for lox, or shaped into a fishcake as an alternative to hamburgers. But while salmon is enjoyed all over the globe, it also swims at the center of controversy, with commercial fishing, global warming, and loss of freshwater habitats all threatening salmon populations...