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Thermolicer. Image: Linn Therese Skaar Hosteland.
Thermolicer. Image: Linn Therese Skaar Hosteland.

A Thermolicer treatment that caused the deaths of 5,794 salmon at Grieg Seafood Shetland’s North Havra site in November has caused the company to review its lice treatment strategy.

2.5% of the fish treated, which averaged 1.4kg, died during the procedure.

Grant Cumming, MD of the farming firm, explained: “The salmon at North Havra were treated using a Thermolicer hot water treatment. Unfortunately, we had some unexpected mortality during the procedure.  We have investigated the reasons behind the event and have altered our procedures to minimise the risk of it reoccurring.”

He emphasised that the Thermolicer is one of a raft of non-medicinal measures to control lice – including stocking cleanerfish in the salmon sites, installing louse skirts round the cages and shortening the time the salmon are at sea – all of which will help reduce the use of traditional sea louse medication.

“We use these new and alternative treatments as part of our integrated pest management strategy in order to reduce the reliance on traditional medicines. This is important to minimise our impact on the environment and to maximise the working life of the medicines by guarding against resistance, while at the same time ensuring our salmon have a good quality of life free from sea lice infection,” he said.

Thermolicers are produced by Steinsvik in Norway, but the firm were unable to provide any more information on the incident.

"We cannot comment on our customers' concerns and have not received any notification of errors on our Thermolicer," Tore Laastad Steinsvik's sales manager for Thermolicers, told