Frøya Municipality, Norway-based SalMar has released key findings from its “Marine Donut” salmon farm concept, showing promising results for fish welfare and performance.
SalMar took delivery of the Marine Donut in July 2023 from Stathelle, Norway-based aquaculture technology company Bluegreen. The salmon farm – which Bluegreen said is the largest thermoplastics structure in the world – is designed to be fully enclosed to prevent salmon escapes while minimizing risks of disease, algae, and sea lice.
According to Bluegreen, SalMar has performed four successful fish transfers with no issues. Fish welfare during the transfers has been assessed as “good,” with only minor incidents of fin wear likely related to delousing.
“Operational experiences have also led to adjustments in the systems for dead fish removal and feeding, which now function as expected after technical improvements,” Bluegreen said.
The Marine Donut has been operating at full capacity since August 2024 and contains 200,000 salmon.
The company said that the Marine Donut has worked under challenging operational conditions, which revealed the need for a few technical adjustments.
“Water flow measurements indicate that pump system adjustments are required to achieve optimal flow,” Bluegreen said. “Full-scale technical performance measurements will continue throughout the winter, especially to evaluate the structure's response to wave conditions during the season.”
The Marine Donut uses water pumps to create a flow inside the structure to exercise the fish and mimic the environment of a river.
According to Bluegreen, the company had a brief issue with lower water temperatures earlier in 2024.
"That’s a known issue. We draw water from a depth of 40 meters. It maintains a consistent temperature of around 8 degrees Celsius year-round," Blugreen Project Manager Geir Andresen said. "This is in contrast to open net pens, which have warmer water temperatures in the summer and colder in the winter. The fish in Marine Donut will, therefore, have steady growth throughout the year."
Overall, the company said the donut is showing promising results.
“SalMar continues to adjust and optimize the technology as they await the final results of the production cycle,” Bluegreen said. “With positive indications of improved fish welfare, controlled environment, and adaptable technology, Marine Donut could become a key innovation for the future of sustainable aquaculture.”
