Marine fish populations migrate through the fishing territory of more than one country as well as international waters. Fish are traded across the world so consumer choices in one country may affect a fish population on the other side of the globe. Many fish populations are currently under threat from overfishing; consumers need to consider ‘good’ (sustainable) and ‘bad’ fish sources. For some species, fish farming (aquaculture) is proving a positive solution. A global approach is essential if we are to feed a growing world population and manage world fisheries sustainably.