Claiming a first for farmed fish health in Scotland, Scottish Sea Farms has confirmed that no antibiotics were used in any of its farming operations in 2020.

The SalMar and Lerøy Seafood Group-owned producer has been working to reduce its use of antibiotics for several years, with no antibiotics used on its marine farms since 2012, and only minimal use at its freshwater hatcheries in recent years. And then last year, it achieved the milestone of zero antibiotic usage.

This is the result of a holistic approach to fish health and welfare, with vets involved in farm management, Scottish Sea Farms Head of Veterinary Services Ronnie Soutar said.

“We’re very proud to have reached this stage,” he said. “It is important on a global scale that antibiotic use is minimized and only used when absolutely essential, in recognition of concerns over antimicrobial resistance.”

Soutar added that Scotland as a whole typically has low usage, but Scottish Sea Farms has worked to be even lower than the average.

“Scottish salmon farming generally has a very low use of antibiotics compared with other livestock sectors and Scottish Sea Farms has consistently had antibiotic usage well below the sector’s target,” he said.

The company highlighted that in 2016, U.K. non-profit RUMA (Responsible Use of Medicines in Agriculture Alliance) set a goal of 5 milligrams antibiotic active substance per kilogram of salmon produced. This compares to a target of 25 mg per kilogram for poultry meat (broilers) and 99 milligrams per kilogram for pigs. 

In the four years between 2015 and 2018, Scottish Sea Farms averaged 3.6 milligrams per kilogram, but in 2019 this dropped to 0.25 mg per kilogram (5 percent of the sector target), with no antibiotic usage at all in 2020.

“Our use in the freshwater phase of production has been because infections can occur before fish are big enough to be vaccinated. However, new husbandry protocols and major investment in bio-secure facilities are making such infections increasingly rare,” Soutar said.

He also explained that the company would still consider antibiotic use if, in specific circumstances, veterinary advice is that it is essential for the protection of fish welfare.

“The important thing is to keep applying the lessons learned, from dealing with other bacterial diseases, to new threats – that and developing more vaccines to further reduce the need for antibiotics,” he said. “The last year has really confirmed our long-held belief that vaccines are the answer.”

Meanwhile, Scottish Sea Farms is to trial the potential of a new greener aeration system, Flowpressor, to protect its salmon from potentially harmful plankton.

Flowpressor has been custom designed for the aquaculture sector by Poseidon Ocean Systems in Canada. Combining a specially engineered compressors, main distribution lines, and tripod diffusers placed deep within every pen – each pen with its own eight-channel control panel – the new system moves water with lower phytoplankton and higher ambient oxygen upwards, improving the environment within all pens. 

“Flowpressor effectively draws ‘clean’ water from depth of the pen – in other words, well away the planktonic surface layers – and distributes it upwards, improving water quality throughout the whole pen,” Scottish Sea Farms Regional Production Manager for Mainland Innes Weir said. “It also comes with the additional option of ‘bubble curtains’ which create a barrier to plankton and other biological challenges such as jellyfish infestations, significantly reducing the concentration of these potentially harmful organisms within open pen systems.”

The pilot, which will start this month, will see six of the trial farm’s 12 pens connected to the Flowpressor and the remaining six pens served by a standard compressor. 

“We will be looking to see what day-to-day difference the system makes to the feed rate, growth and survival of our salmon overall,” Weir said. “Crucially, we also want to gauge what protection the system can deliver during a plankton event or periods of low oxygen.”

Flowpressor is already in operation along Canada’s west coast, with farmers reporting a 50-60 percent reduction in algae inside the pen, as well as improved fish survival and growth due to fewer lost feeding days. 

Photo courtesy of Scottish Sea Farms 

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