The world is now producing more farmed fish than beef. In 2012, fish production reached a record 66 million tonnes; cattle-farm output levelled out at 63 million tonnes. This ought to be good news for the environment. Cattle farming is one of the biggest contributors to global warming, while fish farming - as well as being sustainable - produces little pollution. Fish such as the silver carp can be reared on existing rice paddies, and they feed on grass, plankton and detritus. Species such as salmon, however, are carnivorous and are fed on smaller fish like anchovies caught in the wild. As a result, salmon can only be farmed by further depleting wild fish stocks. Which one of the following can most reliably be drawn as a conclusion from the above passage?

A Fish farmers who produce carnivorous fish should switch to producing non-carnivorous fish.

B Fish farming is likely to become increasingly more widespread in comparison to beef farming.

C Fish farming will always be better for the environment than cattle farming.

D It would be better for the environment if a greater proportion of farmed fish was noncarnivorous.

E Where possible, farmers should opt for more environmentally friendly forms of farming.