Aeration – the process of pumping air into salmon pens to boost water movement and, in turn, water quality – is one of several protective measures taken by fish farmers when rising levels of plankton are detected during daily water monitoring.
Standard aeration systems use generic industrial compressors to pump in this air, but these can have mixed results. If air flows aren’t evenly distributed for example, then those pens closest to the compressor tend to receive the biggest boost of air.
The Flowpressor system has been custom designed for the aquaculture sector by Poseidon Ocean Systems in British Columbia, where gill health challenges can be more intense with as many as 1.5-2 million cells per litre of algae compared to 50 to 1,000 in Scottish waters.
The system combines a specially engineered compressor, main distribution line and tripod diffusers placed deep within every pen, which each pen having its own eight-channel control panel.
Water with lower phytoplankton and higher ambient oxygen is moved upwards from deep in the water column, improving the environment within all pens.
Innes Weir, production manager for SSF’s Mainland region, said: “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.
“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,” said Weir in a press release.
“Crucially, we also want to gauge what protection the system can deliver during a plankton event or periods of low oxygen.”
SSF said Flowpressor is already in operation along Canada’s west coast, with farmers reporting a 50-60% reduction in algae inside the pen, improved fish survival and improved growth due to fewer lost feeding days.
The system can be set to run 24/7 for routine water quality improvement then moved to protection mode as required, with energy efficiency integral to its design.
Matt Clarke, co-founder of Poseidon Ocean Systems, said Flowpressor was 56% more fuel efficient than standard systems, reducing CO₂ emissions by as much as 700 tonnes for each unit installed.
“That’s the equivalent of taking 150 passenger vehicles off the road for one year,” said Clarke, a former head of engineering for Mowi Canada West.
“Designed for longevity, the system also has an operating life estimated to be three times that of other options on the market, further reducing its carbon, water and waste footprints.”
Stewart Hawthorn, director of Trimara Services, distributor of Flowpressor in the UK, said: “It’s fantastic to see this novel technology being trialled in Scotland for the first time.
“Working closely with Scottish Sea Farms, we have designed a bespoke solution suited to the particular marine conditions of the trial site and look forward to verifying the fish performance gains through the data amassed.”