Seabed conditions and biodiversity 


The world’s growing population will need an ever-increasing amount of food to survive. Our different types of food production will always leave a footprint on the environment, and salmon production will also leave a footprint as it has an impact on the seabed under fish farms.

Lerøy’s ambitions in this area

Our ambition is to create the world’s most efficient and sustainable value chain for seafood by 2025. We aim to produce food without negatively affecting biodiversity and the areas surrounding our farms, such as the seabed and littoral zones.  In other words, we aim to achieve scores from environmental surveys of “very good” or “good” environmental conditions for all facilities.

We aim to identify solutions that allow us to minimise our carbon footprint, secure our future as fish farmers and take responsibility for feeding a growing population.

How we work in the area

Part of our efforts to minimise infection pressure and environmental impact is to have a period of minimum two months every second year during which an individual facility is fallow, cleaned and disinfected. The facilities are divided into zones to allow for coordination of fallow periods. In 2020, each facility was in fallow for 138 days on average.

Feed control is a major part of the efforts to prevent overload. Each cage is fitted with two cameras to monitor the feeding process, so that feeding is stopped when the fish are no longer eating. Dedicated and specialised operators monitor this process continuously. Operators also monitor the number of fish, growth and feed factor to ensure full knowledge at all times of how much the fish in a cage are expected to consume.

How we measure our impact

All fish farms in use are regularly monitored using regular monitoring programs. MOM B and / or MOM C environmental surveys are carried out at least annually in the near zone at each fish farm in connection with biomass peaks / maximum production capacity. These surveys are carried out by independent companies in accordance with NS 9410 and are based on the Aquaculture Operations Regulations.

The MOM B analyses are investigations of grab samples that are collected evenly distributed under the bottom of the fish farm. The surveys are divided into three parts; fauna, chemical and sensory review. Scoring is given from 1- 4 on each parameter on each grab scoop, where 1 is the best result. The total score is the average value of all parameters and grab scoops. If the score is 3 or 4, measures must be taken to improve the condition of the facility.

In addition to B surveys, MOM C surveys are also conducted at all facilities. The C-survey is a trend monitoring of the bottom conditions in the transition zones from the farming zone and outwards in the recipient. This study is based on mapping of fauna on soft bottoms, which is carried out in accordance with relevant ISO standards. In addition, hydrographic, geological and chemical support parameters are included. These extended trend monitoring outside the local areas is done at least every 5 years, but the frequency may increase based on the condition from each survey.

Targets per KPI

Max. average MOM B score: 1.5

Share of facilities in coordinated fallow zone: 100%

Result: All the facilities are included in the coordination zones for fish health and fallow periods.

Average number of days fallow per facility: 130


Result per KPI  


Share of facilities in fallow zone 

Average MOM B

Average days fallow


100 % 




100 % 




100 % 




Action taken due to results per KPI

On the basis of results from the MOM B surveys, measures are implemented where this is necessary. There may be reduced production for a period, fallowing, relocation of a site, etc.

A pilot project has been initiated at a marine locality with commercial operations for collection of mud. The objective with this project is to minimise the carbon footprint on the seabed under the facility. This is the first trial involving collection of mud from commercial, full-scale marine facilities.

The project has the potential to contribute to development of new technology for collection in traditional facilities with an open cage system. The project is being conducted in collaboration with STIM, and is partly financed by Innovation Norway.

The Group carries out targeted efforts to shorten production time in the sea by producing large smolt using RAS technology.  As a result, the fish farms will not be in production for as long, and the fallow period for each fish farm will be longer.

In 2013, Ocean Forest was founded together with the environmental organisation, Bellona.  Ocean Forest follows a strategy to achieve more efficient recycling of the unexploited resources in the environments surrounding fish farms. This involves utilisation of waste products from fish production to produce species at a lower level in the food chain. 

Macroalgae and microalgae require nutrient salts to grow, and nutrient salts are a waste product from e.g., fish farming. Shells live off microalgae and other particles in the sea. This allows for more efficient recycling of unexploited resources in the environments surrounding fish farms while at the same time increasing our marine biomass production without having to add more feed or fertiliser and while keeping our seas cleaner.

One of the goals is to study the opportunities for use of mussels or mussel meal as ingredients in feed. Another focus point is to capture nitrogen phosphorous and CO2 from seaweed production.  In 2020, around 300 tonnes were harvested from Lerøy’s localities.