A fibre used to make bullet-resistant body armour and reinforce the cockpit doors of aircraft is being tested by the salmon-farming industry in an attampt to prevent fish breakouts and keep out marauding seals.

It is hoped that nets made of the ultra-strong polyethylene will solve one of the biggest problems for both salmon farmers and conservationists: the escape of farmed fish, with the risk of contaminating Scotland’s dwindling stock of wild salmon.

The first of a series of two-year trials using Dyneema is taking place at a fish farm near Scourie, Sutherland, owned by the company Loch Duart. The pilot is part of a £100,000 industry-wide research and development project co-ordinated and part-funded by the Scottish Salmon Producers’ Organisation. On the Isle of Harris a second experiment is to begin shortly by Marine Harvest Scotland, which is one of the biggest producers of Scottish salmon.

Other funding partners in the project include the Scottish Government and net producers.

The lightweight Dyneema fibre is up to 15 times stronger than quality steel on a weight-for-weight basis, and estimated to be twice as strong as the standard nets used in the aquaculture industry, which are made from nylon or similar materials.

Dyneema floats and is extremely durable and resistant to moisture, ultraviolet light and chemicals. It is an important component in ropes and nets in the fishing, shipping and offshore industries. It is also used for racing sails and cables for tanker mooring.

Nick Joy, managing director of Loch Duart, which produces 3,600 tonnes of salmon annually, said that he had 14 of the experimental nets in place, and the first smolts (young fish) put to sea last month. Loch Duart was the first fish farm to achieve RSPCA Freedom Food approval.

Mr Joy said: “We are delighted to be contributing to this project both financially and by proving this material in the field. The strength of this netting should benefit our production in many ways. Our record on escapes has not matched our high ideals, and this material could be the answer. It is reputed to be less prone to abrasion, and inclined to resist marine growth. We hope these benefits will also yield better growing conditions for our fish.”

Alan Sutherland, managing director of Marine Harvest Scotland, said: “This is an extremely important project to be involved in and one the salmon farming industry and stakeholders will be watching closely.”

Up until now, escapes of fish have been seen as the Achilles’ heel of the industry, as conservationists fear the damage which will be done to wild stocks of salmon. However, the industry maintains that the overwhelming majority of salmon farms have never experienced a breach of containment.

Breaches of containment last year where salmon are known to have escaped represented less than 0.2 per cent of the total farmed salmon in Scottish waters. A recent analysis revealed that about a third of incidents were the direct result of predation — principally seal attack.

Sid Patten, of the Scottish Salmon Producers’ Organisation, said that the nets were twice as expensive as standard ones and that the trials represented a substantial investment.

Andrew Wallace, managing director of the Rivers and Fisheries Trusts of Scotland and Association of Salmon Fishery Boards, welcomed the announcement. He said: “High standards of containment of farmed salmon are important to fish farmers for obvious business reasons — but also to wild fisheries to avoid problems associated with hybridisation with wild stocks.

“It is extremely encouraging to see such a significant investment in this issue and pioneering new technology to address the problem. We look forward to working with the industry on this project and to seeing the results.”

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