Aquaculture has been the world's fastest growing food production technology in recent decades, and continued growth in aquaculture production is predicted. While creating economic opportunity, aquaculture is also a new way of using eco-systems, and there is substantial evidence that aquaculture creates negative environmental externalities. Although the most effective way to address these externalities may be improved governance, this approach is often difficult because most aquaculture production takes place in developing countries with limited management capacity. The fact that a large part of aquaculture production is traded motivates substantial interest in the use of trade measures to reduce environmental impacts. However, the wide variety of species, production practices, and governance systems present in aquaculture makes it unlikely that general trade measures will achieve environmental objectives. Rather, there is a real risk that trade measures will reduce economic opportunity, raise new equity concerns, and impinge on public health with little or no environmental impact.