Environmental Impact

Salmon lice

Lerøy Seafood Group establishes measures for both prevention and treatment of the salmon lice, where a central element is the fish health.

The company has a general strategy for fighting salmon lice, based on the principle of “integrated pest management”, i.e. the implementation of a number of measures to prevent and fight salmon lice, where treatment with medication is the last resort.

The Group’s RD&I work related to salmon lice takes four different approaches:

  1. keep the salmon away from lice
  2. keep the lice away from salmon
  3. destroy the lice before they find the salmon
  4. destroy the lice once they have attached to the salmon

The first three methods are preventive, while the fourth involves treating salmon infected with lice. Lerøy uses all four methods, and has applied for a specific R&D licence to test “packages” of different measures at full scale according to the principle of “integrated pest management”. The work to prevent salmon lice and develop successful methods for non-medicinal delousing is a central element in our work on fish health. Salmon lice still represent one of the major biological obstacles to further development of the fish-farming industry, and activities involving management and control of salmon lice represent a substantial cost driver and have an impact on fish health and welfare.

The Group's salmon lice strategy is sound and shall provide control by means of permanently effective measures, a focus on individual cages at the highest aggregate level and early intervention in situations where the preventive efforts are not sufficiently effective.

SINCE 2011

Prevent infection regionally 

Since 2011, Lerøy Seafood Group has chosen to regionalise the value chain for its own fish-farming production, from release of roe to slaughter, in order to prevent undesired infection by known and unknown agents. As a result, the Group no longer moves live fish by sea between its three fish-farming regions: West Norway, Central Norway and North Norway. This implies major costs for Lerøy in terms of developing regional capacity and ensuring biosafety. We are confident that other enterprises in the industry will recognise the value of introducing similar in-house regulations.

The Group cooperates with other enterprises and research groups to contribute actively towards establishing new knowledge and new tools with which to fight salmon lice. New knowledge and new tools are implemented as they emerge and will form part of the Group's future lice strategy alongside existing measures. Chitin inhibitors are a group of delousing agents used in Norway and abroad to fight salmon lice. At present, it is suspected that chitin inhibitors may cause damage to certain species during ecdysis. The severity of this problem has not, however, been documented, making it difficult to reach a conclusion on the use of chitin inhibitors. Chitin inhibitors have been approved by Norwegian authorities for use to combat salmon lice, but Lerøy Seafood Group has decided to take a precautionary approach. Chitin inhibitors shall therefore not be used unless required due to resistance problems. Special approval is required for their use.

Since 2011, the Group has utilised chitin inhibitors on one occasion at one facility. Lerøy Seafood Group is working hard to achieve its long-term goal of eliminating the use of medicines to combat salmon lice, where justifiable in relation to regulations and factors relating to fish health.

Treatment of salmon lice in 2018 was mainly by mechanical means. Treatment with medication is avoided if possible. The number of  fully grown lice per fish in 2018 was a stabile average of 0,12 lice per fish. 

Main goal: 0 "We work to avoid salmon lice of reproductive age in our fish farms and we want to avoid use of medicines in treating salmon lice infestation."

Important target areas for the future:

  • More intensive use of wrasse than previously
  • Use of alternative release patterns and locality structures
  • Continuous monitoring of release and localities
  • Treatment with approved treatment agents
  • Coordination among facilities
  • Testing of mussels in relation to delousing. 

We aim to achieve this by focusing on three main areas:

1. Prevention

  • Good localities
  • Good smolt
  • Clean nets
  • Common plan for fallow areas

2. Monitoring

  • Counting of lice
  • Notification of lice counts to neighbouring facilities
  • Better communication between neighbouring facilities
  • Effective monitoring can result in the right treatment at the right time and reduce the number of treatments.

3. Treatment:

  • Use of delousing bath – tarp and well boat
  • Feed
  • Wrasse
  • Rotation of medicines
  • General treatment in certain areas correctly timed to suit emigration of wild smolt
  • Treatment in good weather conditions
  • Follow-up and corrective action.

The volume of chemicals used for delousing by Lerøy Seafood Group has fallen substantially in recent years, while the volume nationwide has increased. There has been a particularly high increase in the use of chitin inhibitors nationwide.

chemical used in delousing agents, LSG, active agent


  • Increased use of own-produced lumpfish
  • Optimal utilisation of wrasse
  • Strategic utilisation of treatments
  • Introduction of new methods
  • Limiting infestation pressure
  • Lumpfish production
  • Improved rotation of use of medication over larger areas
  • Large wrasse for parent fish and in areas with more than one generation
  • The capacity to execute treatments within authority deadlines in all localities and coordinated throughout generations
  • Compliance with authority requirements in the regulations regarding lice and zone regulations
  • Cooperation with other enterprises