The appetite for omega-3 fatty acids hailed by studies as a weapon against ailments from heart disease to Alzheimer's to depression appears to be endless. Since 2006, the U.S. market for omega-3 supplements has doubled, to an estimated $1 billion, and that doesn't count the billions of dollars more that consumers paid for infant formula, orange juice, breakfast cereals and a host of other products that have added these wonder nutrients.
But is the fatty-acid craze threatening our ecosystem? The best omega-3 source is oily fish like salmon, mackerel and sardines. Environmentalists fear that some species especially a...