He said that the company has used preventive measures for many years, but that it has now systematised them.
“We have shown many times that it is possible to reduce lice infestation and thus the number of lice. We have now systematised this and created a strategy where we have dynamic use of the various measures,” he told the Lice Conference 2021, held virtually in Norway last week.
In short, the method involves changing the measures through the production cycle in step with environmental conditions such as season, temperature, light, salinity, weather conditions and adapted to the individual locality. Systemised lice control was introduced in September and is being applied in all countries where Mowi farms salmon: Norway, Scotland, Chile, Canada, Ireland and the Faroes.
“It requires that we carry out a real-time monitoring of environmental conditions. It is the prevailing environmental conditions that will govern,” said Trengereid.
The purpose is to always adjust to achieve separation of fish and parasite as much as possible and as often as possible.
Trick the salmon
“We will trick and entice the salmon to stay in certain areas in the cage at all times where the risk of lice infestation is least.
“It may be that the fish should be kept high up with the help of light and feeding if there is a layer of brackish water on top that can also be used curatively. Lice skirts are used when required. Oxygen is added when appropriate. Sometimes it can be right to get the fish to pull down into the cage.”
Mowi has developed six main scenarios. These they have summarised in the figure below.
“We have said that we need three days of stable changes in environmental conditions before we make changes and change scenarios,” Trengereid said.