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Strategy for Improved Pest Control on Irish Salmon Farms


A new report from the Irish Department of Agriculture Fisheries and Food looks at fresh strategies for controlling sea lice in farmed salmon.

Executive Summary

Marine finfish production in Ireland grew steadily throughout the 1990s; production in 2001 reached a high point of 24,000 tonnes but declined to 13,318 tonnes by 2006, due in some part to a lack of profitability and consequent liquidity in the sector. 2007 saw a small increase in production levels to 13,800 tonnes. The Minimum Import Price (MIP), a trade correction measure introduced by the European Union in 2005, has stabilised farmed salmon prices in a market which was being distorted by below-cost-selling in the European market. The MIP has provided the Irish industry with an opportunity to trade its way back to prosperity and to a position where it can once again increase output. The Irish industry acts as an important socio-economic driver in a number of rural and coastal communities by providing a source of local employment both full time and seasonal.

Farmed salmon is now the most commonly eaten fish in Europe, because of its year round availability and its versatility from a culinary perspective.

The ecto-parasitic sea louse, a tiny crustacean, is an economically significant pest of the farmed salmon industry worldwide. It is important, both from a farm management point of view and in the context of possible negative interactions with wild migratory salmonid populations, that this pest be tightly controlled. Accordingly, a mandatory national sea lice monitoring and control regime regime which features so-called ‘treatment-trigger-levels’ has been put in place, which aims to keep the level of infestation on marine salmon farms as low as possible. Achieving the desired level of control of this parasite has proved to be a challenging proposition in some areas in recent years.

The pest has shown itself to be very resilient and it has the ability to rapidly develop resistance to the limited range of veterinary medicines that are available to treat it. Levels of infestation were successfully controlled, by and large, through the 1990s, but since 2002/2003 it has been more difficult for the salmon farmers, despite their best efforts, to achieve the very low levels of infestation required by the national control programme. The causes of this difficulty are multifactorial and include: a succession of warm winter sea temperatures, resistance by the pest to the veterinary medicines, limited access to ‘fallowing sites’ for temporal and spatial separation of stocks and other complicating fish health problems.

The control of sea lice has been afforded a high priority by the State since 1991 and Irish salmon farms are the subject of a rigorous and transparent inspection regime carried out by the Marine Institute on behalf of the Government. This monitoring programme is backed up by mandatory licensing requirements imposed on fin-fish farmers through a protocol on management and control.

A Sea Lice Monitoring and Control Working Group was established by the then Department of Communications, Marine and Natural Resources in 2005, comprised of representatives of the Department, the Fisheries Boards, Marine Institute and an Bord Iascaigh Mhara to examine/review the systems and processes for controlling sea lice levels at marine finfish farms. The Group’s deliberations were wholly inconclusive and it was unable to reach any consensus on the way forward at the time of the transfer of aquaculture licensing functions to the Department of Agriculture, Fisheries and Food. Since the establishment of the new Department of Fisheries, Agriculture and Food (DAFF) the Department and the Marine Institute have continued to work on the issue of enhanced sea lice control.

The report outlines a comprehensive range of measures to provide for enhanced sea lice control.

The report makes the following recommendations:

  1. A joint DAFF/industry working group to be established to identify “break out” site options in areas which have persistent sea lice problems. These options would include the possibility of using redundant sites, to optimise fallowing and separation of generations.
  2. Effective and appropriate use of chemical intervention to be reviewed to take ongoing account of changing environmental conditions, developing farming practices, sensitivity of lice to treatments and fish health issues.
  3. The increased availability of well boat capacity coming on stream in the industry to be utilised for controlled bath treatments.
  4. The optimisation of product rotation for strategic treatments should be given further consideration as a matter of urgency.
  5. BIM and the Marine Institute to engage in intensive consultation with the fish farming industry, both with individual fish farmers and representative organisations, to ensure ongoing optimisation of management practices and to report back to the Minister within four months.
  6. BIM and the Marine Institute to immediately establish a working group to report in three months on the potential of alternative treatment approaches and to set out the steps necessary to introduce these approaches.
  7. A national implementation group to be established comprising appropriate representation from:

The Coastal Zone Management, Veterinary and Seafood Policy Divisions of the Department of Agriculture, Fisheries and Food;
An Bord Iascaigh Mhara;
Marine Institute; and
Industry representatives.

The group is to provide the Minister, within six months of its establishment, with a full update of the actual situation on the ground, the progress made to reduce sea lice levels and the further steps required, if any, to redress the situation.

  1. A New role for SBM (Single Bay Management) as a focus for management cells to manage sea lice control at a local and regional level reporting to the national implementation group.

Further Reading

More information - You can view the full report by clicking here.

May 2008