Big fish farms not necessarily most polluting

Fish farm

Half of all fish eaten is now farmed and the industry continues to grow rapidly

Aquaculture industry urged to look at location and management techniques to reduce the environmental impact of rapidly expanding sector

Bigger fish farms do not necessarily have a greater impact on their surrounding marine ecosystems, according to an analysis of Scottish fish farms.

Researchers from Oceanlab at the University of Aberdeen studied data from 50 salmon and cod farms collected by the Scottish Environment Protection Agency (SEPA).

Contrary to popular belief, they found that location rather than the size of the fish farm was a more significant factor in predicting its environmental impact.

Huge growth

The aquaculture industry has trebled in size since 1995, with half of all fish eaten now farm-reared. Scotland has seen rapid growth since the 1980s and now has around 450 licensed farms, almost all producing salmon.

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However, the rapid spread of fish farming around the world has led to concern about its negative impact on marine ecosystems as well as problems including disease, mixing of wild and farmed stocks and chemical use.

Fish farms generate organic wastes in the form of uneaten food and fish faeces. These sink to the seabed and can have detrimental effects on the organisms that live there if they are allowed to accumulate.

Using data that fish farms are legally required to provide to SEPA, Oceanlab researchers were able to assess how the environmental impact of fish farming might be reduced.

Importance of location

'There is a lobby group that just doesn't want big farms, but going by the data we've seen larger farms do not necessarily mean larger impacts,' said Dr Martin Solan.

'Bigger farms tend not to be located in more sensitive areas; there tend to be stronger dispersal tides and they usually have better management techniques such as technology controlling feeding rates and reducing waste,' he added.

Lessons from Scotland

Dr Solan said their findings could help the global farmed fish industry expand while reducing some of its impacts on the marine ecosystem.

'It is clear that fish farming provides one solution to the increasing global demand for food, but the real challenge is how to feed the world with fish without destroying our coastal environment.

'Our findings provide reassurance that Scotland’s fish farming industry has found a way to achieve expansion in a responsible manner. I have no doubt that other countries around the world will follow Scotland’s lead,' he said.

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