Times are tough for shrimpers and fishers in the Gulf of Mexico. The animals they rely on for their livelihood are harder to find. Every summer a dead zone--a region of low oxygen--emerges in the waters along the Gulf Coast. Where oxygen is low, fish and others animals cannot survive. Currently the world has more than 400 identified dead zones, up dramatically from the 49 dead zones identified in the 1960's. The good news is that people can eliminate...