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Growth Only Hinders Aquaculture

A recent study published in Scientific Reports has revealed that the frequency and magnitude of mass mortality events in populations of farmed salmon is increasing in Scotland. It comes on the back of data made available by the Scottish government as part of their Fish Health Inspectorate, which disclosed the deaths of over 17 million salmon last year. In 2022, 55.1 million smolts (salmon mature enough to migrate to the sea) were produced in Scotland. However, the UK’s biggest food export (adding £760 million to the economy and creating jobs for more than 10,000 Scots) has not always been regarded as the pink, oily fish which tastes so good drizzled in teriyaki sauce or wrapped in puff pastry.


Image: Unsplash.

The Picts — an ancient civilisation which inhabited Scotland from around AD297 to the first millennium — revered the silver swimmers as creatures of exceptional knowledge and wisdom. Dedicating intricate rock carvings to the fish, the early Picts refused to eat wild salmon. By 1971, however, the first commercial harvest of farmed salmon in Scotland brought in 14 tonnes of the once god-like fish, rising to 205,000 tonnes per year at present.


In the past, salmon farming faced challenges from parasites and diseases. Nowadays, the industry faces further threats from the human-caused “manufacturing of risk” — a term referring to the paradoxical advancement of production systems and technology despite their tendency to increase population loss. The installation of new technologies which sense changes in water temperatures, currents, oxygen levels, and salt concentrations falsely justify farming in conditions prone to environmental volatility. Combined with fierce competition, financial pressure, and poor regulation, the aquaculture industry has been hurried into a dingy corner where the only obvious escape route is to succumb to the demands of growth through technological advancement.


This has contributed to the intensive farming of Scottish salmon, which was most recently highlighted in a 2023 episode of the BBC’s Countryfile programme. The report showed masses of salmon in cauldron-like cages, the grimy grey water bubbling away as silver bellies floated to the surface. The video showed salmon drifting through the stagnancy, some with empty eye sockets, peeling skin, or rotting mouths. Some could even be seen upturned and bobbing against a moulding net, their gills flaring as if they were gasping for air. It was revealed that infections of sea lice in these farmed populations are particularly difficult to control. Sea lice are parasites which latch onto salmon. These vampiric crustaceans can easily slip through the netting in salmon cages, and previous attempts to utilise their natural predators as a non-chemical control strategy have been unsuccessful.


Unsurprisingly, climate change is also linked to mass mortality events for Scottish-farmed salmon. Rising water temperatures boost the growth of harmful algal blooms — large accumulations of toxin-producing algae ­— which absorb oxygen from the water, leaving less available for the fish. If salmon are already suffering from disease, oxygen shortage only accelerates their dying, in turn producing more dead waste for the algae to feed on and fuelling a vicious cycle. Furthermore, this problem is not just restricted to fisheries in Scotland: mass mortality events have also become larger and more frequent in Norwegian and Canadian salmon farms between 2012 and 2022.


If salmon production is to continue to sustain local and global populations, the aquaculture sector must wake up from the false sense of security it has been lulled into, and rethink its reliance on deceiving technologies and intense production systems. Nevertheless, salmon is undoubtedly important to many people across the world. It is demoralising, however, that the fish whose god-like wisdom was once held in such high regard that the ancient Picts refused to consume it, is now only appreciated for the economic value and flavour of its flesh.

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