Thermolicer delivers encouraging results

Salmon being released back into a pen after thermolicer treatment - Photo: Scottish Sea Farms

THE LOCAL salmon farming industry is quietly confident that an effective and environmentally sustainable method of combatting sea lice infestation has been found.

In the summer, Scottish Sea Farms invested more than £4 million into the first Scottish thermolicer.

Five months later and after having been trialled extensively on Shetland fish farms, including those belonging to Grieg Seafood and Cooke Aquaculture, the industry says the results so far have been very positive.


Developed in Norway, a thermolicer places salmon in warm water at a temperature that kills sea lice but doesn’t harm the fish.

Biologist Noelia Rodriguez oversees the thermolicer use on Scottish Sea Farms' Shetland sites - Photo: Hans J Marter/Shetland News

Mounted on board the Voe Viking, a boat on long-term lease from Delta Marine, the thermolicer was berthed at Blacksness Pier in Scalloway earlier this week.

Andrew Moncrieff, one of the local operators, said they usually treat up to 40 tonnes of salmon per hour.

The fish are pumped on board into three large holding tanks, and after the cold water has drained away and cleaner fish such as lumpsuckers have been separated, the salmon swim through a network of pipes with water 20 to 22 degrees higher than the sea water temperature before being released back into the pens.


Scottish Sea Farms says the treatment, which takes no longer than one minute per fish, removes between 95 and 98 per cent of sea lice. During that time the salmon is exposed to the warmer water for around 30 seconds.

Operator Andrew Moncrieff monitors the temperature salmon is exposed to - Photo: Hans J Marter/ Shetland News

The company’s animal health biologist for Shetland, Noelia Rodriguez, said as well as being gentle on the fish, the method has the added advantage of also removing the parasite from the environment.

“The temperature shock will take the lice off the fish and kill the lice. For the fish that is not a problem, but for the lice it is,” she said.

“We can use it on any size of fish from small to larger ones; it is a clean method, and it doesn’t involve medicines.


“We do not just remove the lice, we are also capturing the lice, and so no lice will go back into the sea. Over time you will definitely get a lower burden in the environment.”

Salmon farming companies are investing heavily into a number of different sea lice treatments, such as cleaner fish (wrasse and lumpsucker) or hydrolicer technology, which uses low pressure water jets to dislodge sea lice, all in an attempt to improve the health status of stocks, and reduce losses inflicted by the parasite.

One single sea louse left in the filter - Photo: Hans J Marter/ Shetland News

In October, the Scottish industry was successful in attracting £1.76 million of European funding towards developing technologies to control sea lice, coordinated by the Scottish Aquaculture Innovation Centre, which is based at Stirling University.

As fish health improves with successful sea lice treatment, salmon will be able stay and grow in the pens for longer, and therefore the economic advantages could be considerable.

Rodriguez added: “The operators in Shetland are working together as we are sharing growing areas around the isles. It is very important for all of us to do this at the same time.”

“Medical treatment will continue to be part of the toolbox, probably less so, but it will still necessary because there are cases in which you will not be able to use the thermolicer.

“So far the experience is really positive. All the farms agree that this is the best sea lice treatment we have had so far.”


The local manager of the Scottish Salmon Producers’ Organisation, David Sandison, added: “This is one of the new developments in what we call mechanical sea lice control.

“The so far very encouraging results are good for the industry overall, because it adds to the range of things that we have at our disposal to deal with a problem that we have to find and develop continuously new solutions for.”