What are Sea Lice?
Sea lice are a parasite found on fish world wide. There are two species of sea lice commonly found on cultured salmonids, Caligus elongatus Nordmann, which infests over fifty different species of marine fish, and Lepeophtheirus salmonis Krøyer, which infests only salmon and closely related species such as rainbow trout.
What effect do sea lice have?
Sea lice are regarded as having the most commercially damaging effect on cultured salmon in the world with major economic losses to the fish farming community resulting each year. They inflict damage to their hosts through their feeding activity on the host's body. Sea lice affect salmon in a variety of ways; mainly by reducing fish growth; loss of scales which leaves the fish open to secondary infections; and damaging of fish which reduces marketability.
How are sea lice monitored?
The Marine Institute is charged with carrying out regular inspection of sea lice levels around the country in accordance with the Department of Marine and Natural Resources Framework on Aquaculture Monitoring, Protocol No.3:Offshore Finfish Farms - Sea Lice Monitoring and Controls(PDF, 32KB).
All fish farms undergo lice inspections 14 times each year. One lice inspection takes place each month at each site where fish are present, with two inspections taking place each month during the spring period-March, April and May. Only one inspection occurs for December / January. At each inspection two samples are taken for each generation of fish on site. Thirty fish are examined for each sample.
Sampling is divided into 3 regions, the west (Counties Mayo and Galway), the north-west (Co. Donegal) and the south-west (Counties Cork and Kerry).
The results are published annually. These reports are available to download from the Marine Institute library. The most recent is National Survey on sea lice on fish farms in Ireland 2008 (PDF, 1.8Mb).