Permeable fabric 'keeps out more than 99% of lice larvae'
Use in six-metre-deep skirts in Chile has reduced medicinal treatments by up to 50%
Tarpaulin “skirts” can play an important role in limiting the number of sea lice infesting farmed salmon, but wrapping a pen with an impermeable barrier has the disadvantage of reducing water exchange and dissolved oxygen.
Now, a study of a permeable lice skirt material in Chile has found that it blocks 99.6% of nauplius-stage larvae and 99.7% of copepod-stage larvae of the Chilean louse Caligus rogercresseyi while still allowing adequate water flow.
The study of the X12 fabric made by Indian net maker Garware Technical Fibres was carried out by the Austral University in conjunction with Mowi Lab Chile.
Bigger mesh for Norway
“Our R&D department developed a three-dimensional fabric with an opening of 80 to 150 microns for Norway, and a second generation of 60 to 100 microns for Chile, given that the local sea lice is smaller, thus generating a product applied to the Chilean market,” said Marcos Jofré, business associate at Garware.
The company said six-metre-deep lice skirts made from the X12 fabric are being used on 15-metre-deep cages without the need for oxygenation. More than 80% of Caligus are found in the top six metres of the water column.
Experience in the field shows a decrease in the frequency of medicinal delousing baths of up to 50%, with a reduction in lice of up to 60%, reports Garware.
“The reduction in the frequency of chemical use is in itself a desired goal, not only because of its cost, but also because it lengthens the useful life of the chemicals, delaying the generation of resistance by the parasite. We know that monospecific strategies, based exclusively on chemicals, have shown the generation of long-term resistance,” said Francisco Serra, commercial manager for Garware in Chile.
'Outstanding partners'
The fabric is also being used in Canada, by salmon farmers Grieg Seafood, Mowi, Cermaq, and Cooke Aquaculture, and has the approval of Cermaq Canada innovation director Brock Thomson.
“Cermaq Canada operates in the traditional territory of the Ahousaht First Nation under a robust agreement, which sets out high expectations for our performance and accountability,” said Thomson.
“A major component of that agreement focuses on sea lice mitigation and management; we have committed to meet or exceed those high expectations, and we need a robust set of tools to accomplish that. The Garware X12 lice shield has made a significant contribution to our sea lice management since 2022, and their team has been outstanding partners in navigating the challenges and the successes of implementing this technology in Canada.”
Semi-closed containment
Garware is also offering the X12 fabric via its agents in Scotland and Norway.
Although it has so far only been used as a lice skirt, it could also be made into a bag for semi-closed containment, the company told Fish Farming Expert.
Asked if there were circumstances where oxygen supplementation would have to be used with X12, Garware said: “In the event of an anoxic tide, in which dissolved oxygen is depleted, it could be supported with oxygen injection.
“Lack of oxygen may be a condition of a certain aquatic environment, not of the product.”
