It seems as more and more of the fish available to us in the supermarket and in restaurants is farmed. Is this good or bad? Probably a bit of both. Raising fish in fish farms doesn’t impact the wild fish to any great extent, but fish farms must be well situated, and well run to prevent problems. They are not natural ecosystems!

Aquaculture has become a booming industry in Chile, with salmon and other fish farmed in floating enclosures along the South Pacific coast. But as farmers densely pack these pens to meet demand, diseases can easily pass between fish — for example, an outbreak of infectious salmon anemia that emerged in 2007 caused the deaths of more than a million fish and threatened to cripple the industry. And unsustainable aquaculture methods can have a wider impact, spreading disease to the world’s already vulnerable ocean fisheries and contaminating the environment.