A CUSTOM-DESIGNED air processing system already being used in Canada is to be trialled in Scotland to deal with plankton which is potentially harmful to farmed salmon.

Scottish Sea Farms is to test the greener system, Flowpressor, to protect its salmon from what it called a major threat to the health of farmed fish worldwide.

Many species and concentration of plankton are vital to a healthy ecosystem, but others can harm humans and animals.

In the case of farmed salmon they can cause damage to the gills and deprive the fish of oxygen.

Aeration is the process of pumping air into salmon pens to boost water movement and quality, and is one of several protective measures taken by salmon farmers when rising levels of plankton are detected during daily water monitoring.

Standard systems use generic industrial compressors to pump in the air but with mixed results.

If air flows are not evenly distributed for example, those pens closest to the compressor tend to receive the biggest boost of air.

The Flowpressor system, in contrast, has been designed for the aquaculture sector by Poseidon Ocean Systems in Canada, where gill health challenges can be more intense with as much as 1.5-2 million cells per litre of algae, compared with 50 to 1000 in Scottish waters.

This new system moves water with lower phytoplankton and higher ambient oxygen upwards, which improves the environment within all pens.

Innes Weir, Scottish Sea Farms regional production manager for mainland, said: “Flowpressor effectively draws ‘clean’ water from depth of the pen – in other words, well away from 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 programme will start later this month, and will see six of the trial farm’s 12 pens connected to the new system while the remaining six pens are 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.

“Crucially, we also want to gauge what protection the system can deliver during a plankton event or periods of low oxygen.”

Farmers along Canada’s west coast already using Flowpressor have reported up to a 60% reduction in algae in pens, improved fish survival and growth, due to fewer lost breeding days.

Poseidon’s co-founder, Matt Clarke, said: “Not only is Flowpressor more effective at protecting farmed fish health than standard systems, it’s also 56% more fuel efficient, 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.”