Wild-Caught Fish More Sustainable than Farmed - New Report Shows

Fish farming is often portrayed as a sustainable solution to feed a growing population and protect wild fish stocks – but this is not true.

It has been argued that fish and crustacean farming is sustainable because it uses relatively little wild fish for feed and has improved over time. But a new report published in Science Advances contradicts that thesis – big time. The researchers have done calculations in a completely new way and can now show the actual amount of wild-caught fish required to produce the farmed fish. And it is much more than the industry had previously claimed.

It takes between 4 and 5 kilograms of wild fish to produce one (1) kilogram of farmed salmon, according to the new calculations, and therefore, the researchers argue in the report, can never be a substitute for wild salmon, nor can it protect wild salmon from extinction.

To calculate how much wild-caught fish is used for fish farms, the ratio FI:FO fish-in:fish-out is used, i.e. the sum of how much fish is used (FI) is divided by how much fish comes out (FO). It sounds simple, but there are many aspects to consider that complicate the calculations.

What the researchers have done is to include all the elements involved in the production of fishmeal and to use more sources to do so than before, thus obtaining more robust figures than before.

For example, they have taken into account the actual amount of fish used in processing, including that which is gutted and that which is not landed on the boats but dies because it is thrown overboard, or otherwise lost in processing en route. And they found that the percentage of fish used for farming is between 27 and 307 per cent higher than previous estimates.

– They show that the use of fishmeal and fish oil in aquaculture is more complex than many industry analysts have estimated, says Stefano Longo, Institution of sociology and labour studies of the University of Gothenburg.

– The input of fishmeal and fish oil in aquaculture systems has probably been underestimated, and perhaps even greatly so.