Tests show good health for fish in ‘Marine Donut’
The first full test of an innovative closed-containment system for salmon farming has shown good outcomes for the fish, with mortality of just 0.8%.
The "Marine Donut", developed by Norway-based engineering firm Bluegreen, is a floating closed farming facility made from HDPE (high-density polyethylene) material. It has been designed to protect against challenges like sea lice and fish escapes.
The first version of the Marine Donut was delivered to SalMar in 2023 and the facility is now operational at Seterneset, near Molde.
The company has been granted a development licence through the Norwegian Directorate of Fisheries’ scheme for innovation in aquaculture. Under the licence, Bluegreen will conduct two full-scale tests with food fish, both involving thorough documentation and evaluation of various technical and biological parameters.
In the first full-scale test, 195,000 salmon with an average weight of approximately 3 kg were introduced into the Marine Donut in three separate batches. After 101 days, the facility was emptied, and the salmon were sent for processing.
Bluegreen said results of the first test, carried out in association with salmon producer SalMar, have been very promising.
Geir Andresen, CCO at Bluegreen, said: “This full-scale test has provided valuable data and insights that will be crucial for further development of this groundbreaking technology.”
SalMar has prepared an interim report from the first production cycle. According to the report, several measured parameters confirm that the Marine Donut performs as expected.
- Water Quality: Monitoring has shown good levels of oxygen, pH, salinity, and temperature. Some challenges related to turbidity (water clarity) measurements were identified, but these are being resolved and have not impacted the water quality inside the pen.
- Fish Health and Welfare: Overall, the fish have exhibited good health and low mortality rates, despite carrying pancreas disease (PD) into the Marine Donut. Comprehensive monitoring of fish welfare has been conducted, including assessments of wounds, cataracts, and deformities, as well as gill health and stress levels (measured through feces samples). All results indicate very good fish welfare.
- Technical Performance: Water exchange has functioned well, but some adjustments were necessary after discrepancies were observed between measured and calculated current speeds. The system has been improved along the way to optimise performance.
In October, the facility was emptied of fish, and 195,000 salmon were sent for processing. The extraction went very smoothly, Bluegreen said, with minimal stress for the fish.
"When emptying the Marine Donut, we raise the facility by about 20% and connect it to the well boat. Then, it’s tilted by 4 degrees," explained Andresen. "This ensures good water flow and optimal conditions for the fish throughout the process. At the same time, we gradually reduce the water volume to keep the fish’s environment stable for as long as possible."
The company now anticipates that the upcoming launch of the Donut will quickly fill its production capacity, and says it is now accepting orders on an ongoing basis.
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