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Aquaculture: farming the sea

Undersea nets used in offshore fish farming Undersea nets used in offshore fish farming Adnan Buyuk
07 Apr
Increasing interest in offshore aquaculture is dividing environmentalists

What is offshore aquaculture? Aquaculture involves raising fish or shellfish in floating pens in bodies of water: farming fish as opposed to catching them in the wild. It accounts for just over half of the world’s seafood and is the fastest growing sector of food production. The ‘offshore’ part is a little trickier to define.

‘There is no global consensus about what “offshore” means exactly,’ says Halley Froehlich, a postdoctoral researcher of sustainable aquaculture. ‘In America it means operations located between three and 200 miles away from the coast, however, worldwide it means fish farms that are generally deeper and further at sea, crucially in places with a faster current.’

According to Froehlich’s research with the University of California, Santa Barbara, interest and investment in offshore aquaculture is increasing ‘at a rapid rate’. The main hope is to reduce the environmental issues of coastal aquaculture, such as introduction of diseases, pollution and pests (sea-lice, for example), by moving them further away from sensitive shorelines. Further at sea, and at deeper depths, the water movement is often faster, movement that supporters say will flush out waste and minimise pollution. ‘Carried out in a sustainable way, alongside scientific research, offshore aquaculture could mitigate some of the environmental issues of near-shore farms, at a higher rate of production,’ says Froehlich. ‘Done effectively, a small area of the world’s oceans could provide essential sources of protein for a growing population.’

Critics of offshore farming claim that moving further into the ocean would simply transport the same issues to areas where they could be harder to monitor and regulate. ‘Out of sight, out of mind,’ says Hallie Templeton, Senior Oceans Campaigner at Friends of the Earth, which has a strict position on industrial ocean fish farming. ‘Pollution, disease and pests would still be spread into the surrounding waters, whatever the depth,’ she says. ‘That is the nature of a free exchange between water and the pens.’

Others also point to the greater exposure of offshore pods to more powerful weather and water speeds, increasing the risk of all the fish escaping – known as ‘spills’. In fact, the US state of Washington is in the process of phasing out its non-native fish farms after a high-profile spill released more than 260,000 Atlantic salmon into its Pacific waters. Templeton suggests other alternatives, such as recirculating farms, which raise fish in tanks onshore and use their waste to fertilise plants, keeping the waste away from the wild ecosystems.

So far, most offshore farms are experimental projects in countries with an established aquaculture industry, such as Norway and the US. However, for the past two years, the US’ National Oceanic and Atmospheric Administration has been authorising offshore permits for the Gulf of Mexico in the hope of encouraging commercial operations. Froehlich believes this is part of an inevitable move offshore: ‘It will not be a panacea to all the problems of onshore. However, this makes it all the more crucial for scientists and conservationists to be involved in working out what is sustainable aquaculture practice.’

This was published in the April 2018 edition of Geographical magazine.

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