The first full-scale production cycle of Marine Donut was completed in October 2024. The final report from SalMar summarizes experiences and measurements from the monitoring program carried out in accordance with the Norwegian Directorate of Fisheries’ requirements for development licences.
The purpose of the monitoring program was to document how Marine Donut performs in operation, with particular focus on the water environment, fish welfare, biological results, and technical performance. The program was largely carried out as planned, with a few minor deviations described in the final report. SalMar was responsible for implementing the monitoring program and has prepared the final report.
Read the full final report here (Norwegian only)
Water quality and environment-based parameters were closely monitored throughout the entire production cycle. Oxygen levels, temperature, salinity, pH, turbidity, CO₂, and algae content were measured daily in accordance with the monitoring program. The measurements show that water quality in Marine Donut was good and stable throughout the period.
Observations and measurements indicate that the intake and mixing of fresh water function well within the fish volume. The donut-shaped design of the unit, combined with multiple intake points and a rotating water flow, provides even oxygen levels throughout the entire enclosure.
Production cycle 1 ran from July to October 2024. Three successful fish transfers were carried out, with a total of approximately 195,000 salmon. The transfers were completed efficiently and without fish welfare–related challenges.
The operational experience has provided valuable learning. Among other things, it was identified that water velocity along the bottom of the fish volume was lower than expected, which affected the transport of dead fish. Measures such as increased thrust on mixers and adjustments to their positioning were implemented and contributed to improvements. However, it has periodically been necessary to use an ROV to ensure satisfactory dead fish removal.
Feeding in Marine Donut generally works well in terms of feed distribution, but it is challenging to assess appetite and feeding activity using fixed cameras—particularly at high biomass and under reduced lighting conditions. This is an important area for further improvement.
Crowding and harvesting of fish using the ballast system functioned as intended. During harvesting of large biomasses, additional oxygenation was required in addition to the permanently installed equipment.
Fish health and welfare were followed up through regular inspections, welfare scoring, and monitoring of gill health. An outbreak of pancreatic disease (PD) was detected in the fish group, but mortality remained low.
Fin erosion, cataracts, and eye damage were recorded on a weekly basis. Stress measurements based on cortisol levels in feces showed no signs of elevated stress. Observations of fish behavior indicate that the salmon had sufficient access to air for swim bladder inflation.
Production data show that appetite was good at the start of the period. Increased stocking density had only a limited negative impact on feeding. However, the PD outbreak in August led to reduced appetite and lower growth than normal.
Mortality during the period the fish were held in Marine Donut was low. In total, 190,388 fish were harvested with an average weight of 4,659 grams.
Harvest results show a superior share of 93.5%. Downgrading was mainly due to sexual maturation and a small proportion of deformities—conditions not related to production in Marine Donut.
The data and communication systems functioned as planned, and measurement data have been stored in accordance with requirements. Full-scale measurements of water flow in the fish volume have been completed. Measurements of hydrodynamic pressure, global movements, and mooring forces are ongoing and will be presented in separate final reports.
The final report from the first production cycle provides a solid factual basis and valuable experience for the continued development and optimization of the Marine Donut concept.
