Fish health and fish welfare


Farming fish entails responsibility for ensuring that the fish have the best possible conditions. The challenge is to provide for the best possible way to protect and ensure fish health and welfare. The most significant difficulties in recent years have been Sea lice, bacterial wounds, injuries from handling, CMS, loss of circulation and gill disease

Our ambitions in this area

We want the fish in our cages to thrive, and aim to protect them as much as possible against unnecessary impact and stress. We care about our fish, and willingly accept the ethical responsibilities inherent in farming fish. Our ambitions are also to make use of procedures to standardise the processes to which the fish are subjected, and to update these as soon as we gain and implement new knowledge. As such, the entire organisation has rapid and efficient access to new knowledge.

How we work in the area

We work with fish health and fish welfare in a number of areas throughout the farming value chain. Lerøy works on the following initiatives in this area:

  • Fish welfare training courses for all employees who handle fish
  • Lice counts, weighing for average weights and individual control only performed on anaesthetised fish
  • Optimised nutrition
  • Optimised breeding programme
  • Optimised environmental conditions
  • Optimised cleaner fish farming, handling and feeding
  • Identify solutions for improved handling of fish
  • Screening for known pathogens when moving fish
  • Biosecurity protocols and Veterinary health plans for all sites, which are followed up, at least with a routine based monthly health control by authorized fish health personnel
  • Controlled processes for handling the fish through the harvest process (including electric or percussion anaesthesia prior to bleeding, and no use of CO2

Lerøy works continuously with welfare indicators by adapting all parts of production in order to ensure optimal fish welfare. As part of our ongoing improvement measures, we make use of several international standards relating to fish welfare and biosafety.

The welfare indicators registered daily are temperature, oxygen, growth, density and category for cause of death. The welfare indicators we measure at regular intervals are lice, gases, salinity, visibility, current, vaccine side-effects, outer blemishes, cataracts, gill status, algae, jellyfish, agents and sedimentation under the facility.

The different welfare indicators have provided us with the opportunity to objectively measure and compare what the different parameters indicate about overall fish welfare. This allows us to make interventions in production in order to prevent factors that impair fish welfare.

All facilities are monitored every month with control/visits by authorised fish health personnel. The purpose of these controls is to identify any room for improvement. Extraordinary controls are also performed, with follow-up and sampling when mortality is higher than normal at the facilities.

Efforts are always made to minimise the amount of time the fish are out of the water for vaccination and sorting. Vaccination procedures include strict limits on how long the fish are on the vaccination table, based on air temperature. The injection point and amount injected are controlled regularly during vaccination to ensure that the vaccination is correctly administered. This is important with a view to reducing the risk of negative consequences for the fish later in life caused by side effects from the vaccine.

We calculate a fish welfare score before and after treatment for all non-medicinal delousing. This provides us with documentation of the scope of the impact, and whether we have to take action to reduce the negative consequences.

The fish are monitored throughout every part of the slaughter process by personnel who have received the obligatory training in fish welfare. All fish are anaesthetised before slaughter, either by electric shock or a blow to the head. The system and method for slaughter require the follow-up of the Norwegian Food Safety Authority. Every day before starting slaughter procedures, the fish are checked and logged to verify a sufficient level of anaesthetisation.

How we measure our impact

On a daily basis, all facilities electronically register the number of dead fish and the cause of death.

Targets per KPI and Results per KPI

Target 2021: Survival in sea, last 12 months according to GSI: 94,5%

Result 2021:92,5 %

This is mainly due to challenges involving stress and injury of treatment/handling, tenacibaculum infections, viral disease and wounds.


Results, past 3 years:    





Survival in sea (%)




Survival on land (%)





TARGET 2022: Survival of groups after completed production cycle: 89%

Number of outbreaks of disease

The list specifies dead fish by number and by biomass for the six major categories of mortality.




Number of dead fish

Dead fish, in tonnes













Bacterial Wounds








Number of dead fish

Dead fish, in tonnes

Bacterial wounds









Mechanical injuries



Loss of circulation



Gill disease






Number of dead fish

Dead fish, in tonnes










Bacterial wounds



Mechanical injuries



Loss of circulation




What action has been taken

We make use of procedures as governance tools for production. These procedures help us standardise the processes to which the fish are subjected, and they are updated as soon as we obtain new knowledge that has to be taken into account. As such, the entire organisation has rapid and efficient access to new knowledge. 

Juvenile fish

Pumps, pipes, sorting equipment, vaccination equipment and hoses are checked at regular intervals, and any faults or defects are rectified before the equipment is used.

For major operations such as vaccination and sorting, the fish are inspected for any damage at regular intervals in order to detect faults in the equipment.

All components used for release of fish are inspected regularly. If we detect an increase in mechanical damage, we stop deliveries until we have discovered and, if necessary, rectified the cause of the damage.


When releasing smolt into the sea cages, dead fish are inspected for mechanical damage that may have occurred during transport. If we uncover an increased volume of mechanical damage to fish, the delivery process will be subjected to review.

If the different forms of handling fish involve crowding, we follow a procedure describing how to carry out such activities.

We calculate a fish welfare score before and after treatment for all non-medicinal delousing. This provides us with documentation of the scope of the impact, and whether we have to take action to reduce the negative consequences.


A number of projects have been implemented to improve fish health and fish welfare. These include:

Oxygenation in sea cages project: Det er ønskelig å undersøke om det er mulig å stabilisere oksygenverdiene i en merd ved å tilsette oksygen. Vi ønsker og å undersøke om mer stabilt oksygennivå i en merd gir bedre fôrutnyttelse og bedre helsestatus på fisken.

Fôringrediens og motstandsdyktighet mot CMS: Status score 4. Det er ønskelig å undersøke om endret fôrresept kan gi økt overlevelse og bedre tilvekst ved CMS påvisning.

Lerøy internal wound projects: Different projects that aims to reduce prevalence of bacterial wound-infections. In 2020, a project was implemented to identify risk factors for wound development on large fish and fish recently released to sea.

Vaccine trials: Contribute to development of new/more effective vaccines.

R & D license and Prolaks project: Aims to map effect of post smolt size on health, welfare and performance.


FHF 901736 – Knowledge base of biological relevant welfare indicators for salmon in aquaculture (BIORELEVANS): Aims to provide necessary biological knowledge for establishing health- and welfare data from automatic scanning. Establish limits for when different indicators reflect a normal situation.


FHF 901434 - Tenacibaculum spp. Project: Aims to increase knowledge of tenacibaculosis, identify risk factors of disease, describe toxin production and perform trials with use of toxins as antigens in vaccines.


Lerøy internal robust smolt project: Aims to find the causes of some smolts developing poorly and after sea transfer.


FHF 901680 Pasteurellosis in norwegian salmon: Characterizing, epidemiology and dynamics of pathogen transmission.


Prevention of salmon associated Pasteurella project: Aims to find effective preventive treatment against Pasteurella.


Pathogen project: Aims to map infection pressure of a number of pathogens during the production cycle, including finding risk levels for transmission of disease by vectors.


Welfare project: Aims to map fish welfare related to different “non-medicinal” treatments.


Lerøy internal project: Aims to increase survival rate and robustness of fish in smolt production.


Lerøy internal project: Aims to increase survival rate and growth in sea.


Lerøy internal project: Aims to find measures to reduce risk for mechanical injuries to fish.