Salmon aquaculture
An open-cage salmon farm in Loch Fyne
challenges of a changing climate, low carbon emissions and water use are valuable attributes.
However, one difficulty lies in determining the relative importance of different environmental impacts: in other words, do the low-carbon and water- saving benefits of salmon farming justify the environmental and ecological degradation? Reducing our carbon footprint is essential for tackling climate change, but so too is the carbon-storing potential of healthy marine ecosystems. It is inevitable that the salmon farming industry in Scotland will continue to expand, but the key question is how this expansion will, or rather should, take place. The current practice of open-cage farms that directly impact the surrounding marine environment cannot be considered the future of salmon farming. Alternative technologies must feature if salmon farming is to expand and be sustainable.
There are two alternatives – semi-closed and closed farms – that are most often highlighted and there are compelling arguments in favour of both. Semi-closed farms remain located in the sea, but a combination of physical barriers separating farmed fish from the surrounding waters, waste collection systems, and water pumps significantly reduce the environmental impact. Closed systems, meanwhile, are effectively salmon farms on land, where every aspect of the environment is controlled with water pumps, biofilters
and thermostats to recreate salmon’s natural environment. This enables salmon production to take place anywhere in the world, with farms potentially located closer to markets, which would in turn reduce transportation costs and emissions. However, there are challenges with both of these systems that prevent widespread introduction. Open-cage farms have low carbon emissions and
water-saving benefits of salmon farming justify the environmental degradation?
water use precisely because water exchange and waste disposal are services provided at zero financial cost by the sea (although there is, of course, an environmental ‘cost’). As soon as a barrier is placed between farmed fish and the surrounding environment, water pumps and waste management are required, which significantly increases energy consumption.
Additionally, water consumption is also a concern. While semi-closed systems can pump water from the
Do the low- carbon and
surrounding sea, closed systems on land require water to be provided.
The extra cost of increased energy and water consumption, along with the start-up funds required to invest in new technology, make both semi-closed and closed systems unattractive to developers and, as such, they are unlikely to be adopted widely. As with all new technologies, semi-closed and closed systems are in the early stages of development; closed salmon farms have only recently begun to produce farmed salmon at a small scale but are not ready for the large scale the market requires. While the widespread use of closed salmon farms is unlikely to happen in the near future, there is already interest in semi-closed systems in Scotland – with one application in progress in Loch Long, Argyll. In time, it is expected the costs of closed and semi-closed systems will drop, making both more viable.
The socio-economic benefits of salmon farming are sufficient for Scottish Ministers to back expansion, but environmental, economic and market drivers will play important roles in exactly how that expansion takes place. The most likely scenario is a future that contains a combination of all three systems which will evolve depending on technological advancements, financial incentives and improvements in our understanding of environmental impacts.
Dr Sam Collin is the Trust’s Marine Planning Manager.
NOVEMBER 2020 SCOTTISH WILDLIFE 29
© Richard Johnson/Adobe Stock
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