Norwegian salmon industry struggling with “explosive” growth in sea lice, a world wide problem

A recent press release from the Norwegian Institute of Marine Research said sea lice numbers have never been higher in northern Norway than they are now. "In the north, we saw an explosive increase and doubling of the number of louse larvae this summer," researcher Anne Dagrun Sandvik said.

Sandvik placed the blame for the explosion in lice production on warmer water and said salmon farmers measuring the temperature in the north at a depth of 3 meters found temperatures to be much higher than normal.

"The temperature at 3 meters has been 3 to 4 degrees [Celsius] above what is usual in the north, which has given the lice a huge advantage," she said. At higher temperatures, sea lice life cycles progress faster, allowing lice to become adults sooner and multiply.

(Read the report in Intrafish, 13 September 2024)

Lice are increasingly a world-wide problem, leading one veteran industry observer to say that it is time to "close down the industry" in favour of closed systems (Intrafish, 4 October 2024).

Sea lice attach themselves to salmon and feed on their skin, blood and mucus. Young salmon are particularly vulnerable. Sea lice infestations can affect salmon growth through lower energy reserves in the liver, impaired cardiac function, and heightened stress responses. Significant infestations can cause open lesions and death, especially in restricted environments like open net pens.

Significant sea lice problems have also been reported in Canada, Chile and Scotland, where  mortalities at Scottish fish farms from sea lice were recently estimated to have cost A$645 million.

A 2011 study found a low incidence of sea lice amongst farmed salmon in Tasmania, but recent independent scientific advice to the Federal Environment Minister reported that "the presence of seals and sea-lice has increased in Macquarie Harbour with the expansion of salmonid aquaculture".

NOFF has anecdotal reports of serious infestations at several leases across Tasmania, but has not been able to confirm these. There is no regulatory requirement for the industry to report lice infestations.