Commercial fish farming has been touted as a way to take pressure off stocks of wild fish, but in fact it has had the opposite effect, according to a study in today’s issue of the journal Nature. Fish farming, or aquaculture, has raised demand for ocean fish such as mackerel and anchovies that are ground into meal to feed farm fish. For every pound of farm salmon produced, two to five times that amount of ocean fish are caught to feed them, say the authors of the study. Fish farming also pollutes coastal areas with large amounts of animal waste. And some domesticated fish have escaped from offshore holding cages and displaced their smaller, wild relatives. Aquaculture has grown dramatically over the past 25 years, and commercial fish farms now produce about one-third of all the fish humans eat.