Introduction
Closed cage farming has the possible to solve the most important environmental challenges in farming of Atlantic salmon. The most immediate benefit is effective prevention of sea lice infestation, thus also preventing the use of harmful delousing methods and negative effects of salmon lice on wild salmonid populations. Lower risk of fish escapees and the possibility to collect and reuse particular organic effluents may also contribute to improved sustainability in salmon farming. The closed systems also show good growth rates, low feed conversation rates and low mortality (Nilsen et al., 2020) . Closed-cage farming enables tighter control of many factors such as water oxygenation level, temperature and hydrodynamic flow. It also allows for closer monitoring of fish health . However, little knowledge exists about how different production intensities in such closed cage systems affect water quality, fish behaviour, fish health and welfare and the final production economy.
Material and methods
In the project BIOCLOSED we have performed a study at a commercial producer of Atlantic salmon in closed cages, where cages have been monitored over a production cycle. The study includes measurements of fish behaviour, water flow and water quality, studies of the development in water microbiome, registration of fish welfare indicators and analysis of key biological and financial data. The main aim is to investigate the effect of two different initial stocking densities on cage hydrodynamic, water quality, fish health and welfare, and to evaluate the economic output during commercial production with such different stocking densities . The project is organized as a cooperation between one Norwegian industrial partner and the research institutions SINTEF OCEAN, the Norwegian Veterinary Institute and the Norwegian University of Life Sciences.
Results
The monitoring at the commercial producer will end in May 2025 and the final results will be ready before the conference.
Litterature
Nilsen , A., Nielsen, K.V., Bergheim, A., 2020. A closer look at closed cages: Growth and mortality rates during production of post-smolt Atlantic salmon in marine closed confinement systems. Aquaculture Engineering , 91, 102124.