Salmon farming, a large employer in the Highlands and Islands, suffered a “record” rise in fish mortalities and fall in production last year, blamed on warming seas and jellyfish blooms.
Scottish salmon is the UK’s top food export with sales worth £578 million in 2022, and a huge domestic market valued at £1.2 billion, according to UK Government figures.
There are over 200 salmon farms in Scotland, almost all based on the west and north-west coasts, due to a presumption in Scottish planning policy against marine finfish farm developments on the north and east coasts to safeguard migratory fish species.
Wild salmon begin their lives in freshwater rivers and naturally migrate to the sea – a process called ‘smoltification’. In aquaculture, juveniles are reared from eggs in freshwater lochs and hatcheries until the smolt stage, when they are moved and grown in nets at sea until harvest.
This month the Scottish Government published its Scottish Fish Farm Production Survey for 2022, detailing how many people it employed and salmon it made. In 2022, 1,508 staff were directly employed in producing Atlantic salmon in seawater – an increase of 13 from 2021. But production plunged.
The industry reared 169,194 tonnes of farmed salmon in 2022, 36,199 tonnes (18 per cent) less than 2021, despite putting more smolts to sea. 2021 was a record year, seeing Scotland’s highest production volume of 205,393 tonnes, up seven per cent from 2020.
“2022 was the deadliest year on record for Scottish salmon farms, with 16.7 million farmed salmon dying in the water,” said Rachel Mulrenan, Scotland director or Wildfish, a conservation charity protecting wild salmon and their waters.
“This year is looking even worse than last, with 10.5 million deaths already reported from January to August; 2.7 million more than the same period last year.”
A WildFish spokesperson added: “Increasingly, fish are reported to be suffering from poor gill health, due to environmental issues, including jellyfish and plankton blooms, as well as parasitic, viral and bacterial infections.”
Ms Mulrenan concluded: “High mortality on salmon farms reflects an environmental disaster, as well as being an animal welfare scandal. Open-net salmon farming is not a viable long-term industry for Scotland.”
Last year the salmon farmers’ trade body, Salmon Scotland, warned of a significant increase in microscopic jellyfish blooms affecting the survival of farm-raised fish.
“Record seawater temperatures do contribute to an increase in naturally occurring organisms which can reduce oxygen levels and also compromise the health of the salmon in areas such as the west coast of Scotland,” it said.
“Jellyfish and algal blooms have been exacerbated this year as a result higher than average temperatures. But these are not expected to last and seawater temperatures are expected to return to average in 2024.”
This month, Salmon Scotland said new figures show improving salmon survival rates, “after several mitigation measures were adopted by farmers to further boost animal welfare amid the climate change challenge, including oxygenation of the water, less time spent in the sea, improved monitoring and new feeding strategies”.
Dr Iain Berrill, head of technical at Salmon Scotland, added: “While there is always a level of fallen stock in any farming operation, the numbers this year are not where any farmer would want them to be. It is utterly devastating to the farmers caring for those animals when any fish are lost.
“Our ability to address the environmental challenges facing our fish while they spend up to two years in the sea has improved, but there is always more we can do to further improve survival.”