Salmon thrive in lice shield trial

THE introduction of lice shields at a Scottish salmon farm has resulted in a healthy crop that has outperformed all previous years.
Scottish Sea Farms installed the preventative measure at its farm at Slocka, Ronas Voe, on Shetland in May 2017.
In the nine months since, sea lice levels have remained below the Marine Scotland Code of Good Practice threshold, and the salmon are showing strong growth and biological performance, said the company.
Specially engineered to suit Scottish marine conditions, each shield consists of a permeable fabric that lets water and oxygen move freely into fish pens while keeping natural health threats out.
This fabric fully encases the pen to a depth of 6m, providing a barrier against sea lice which are most commonly found in the first few metres below the water’s surface.
Such has been the effectiveness of the shields that Scottish Sea Farms has now invested over £800,000 with two Scottish suppliers – William Milne Tarpaulins in Aberdeen and W&J Knox in Ayrshire – in order to roll out similar protection to 11 of its other farms.
The company is also working with neighbouring salmon growers to synchronise the use of the shields, as part of a farm management agreement for those areas.
Jim Gallagher (pictured), managing director of Scottish Sea Farms, said: ‘We strive, wherever possible, to replicate the natural conditions that salmon are known to thrive in.
‘As any farmer will understand, however, this comes with its own risks as the marine environment presents new challenges all the time.
‘We are continually exploring and investing in new ways of dealing with these challenges, and it’s hugely encouraging to see positive early results such as these at our trial project in Shetland.’
This latest advance is part of a wider £11.8 million investment in 2017 by the company to enhance the health and welfare of its salmon – over 85 per cent of which is being spent on non-medicinal approaches.
In terms of controlling the sea lice challenge specifically, key areas of investment include:

  • More than doubling the use of cleaner fish in the last year – 76 per cent of which are now from farmed origin, keeping the company on track to use farmed only stocks by 2020;
  • Developing a new net cleaning pressure pump to keep pens free from marine build-up, simultaneously enhancing fish health and welfare and increasing the effectiveness of cleaner fish;
  • Ongoing investment to increase understanding of cleaner fish, with the insights gleaned being shared with the wider industry;
  • Co-funding new Thermolicer technology that bathes salmon in such a way as to dislodge and catch sea lice, with up to 95 per cent effectiveness.

The company said the need to administer medicines has significantly reduced, with six of its farms requiring no sea lice interventions at all during 2017.
Scottish Sea Farms has also invested approximately £200,000 in environmental data monitoring equipment, as well as more than £260,000 on new underwater camera systems, to combat new planktonic organisms that are potentially harmful to the health of fish gills.
Ralph Bickerdike, head of fish health and welfare at Scottish Sea Farms, said: ‘Even a seemingly slight increase in sea water temperatures of 0.5 degrees can have an impact on the marine environment.
‘This new data monitoring equipment is enabling real time analysis of key markers such as salinity and oxygen concentration, helping us to make informed decisions to maintain high standards of welfare for the fish under our care.
‘Complementing this, the new underwater cameras enable us to observe the fish within the pens and respond swiftly should there be any changes in their natural behaviour.’