The wellboat Ronja Senja in place to transfer the first smolts into the Marine Donut.

15,000 fish provide a filling for the Donut

Floating closed fish farm is stocked with 2.5 kg salmon


The Marine Donut floating closed fish farm being trialled by salmon heavyweight SalMar has been stocked with 15,000 fish with an average weight of 2.5 kilos.

In two weeks, if everything goes well, the farming company will stock a further 185,000 fish. The Donut has a licence for a maximum standing biomass of 1,100 tonnes, which equates to 200,000 harvest-sized fish.

The Marine Donut was designed and built by Norwegian company Bluegreen and has been moored at Sekken outside of Molde since the autumn of 2023 while equipment was tested and commissioned.

A long journey

Thousands of hours have been spent developing the facility, which addresses challenges related to sea lice, escape, and environmental impact by collecting fish sludge.

“It has been a long journey, with ups and downs over many years,” said Bluegreen chief executive Nils-Johan Tufte, who conceived the idea of a torus-shaped fish farm in 2015 and was at the facility to see the fish being stocked on Friday.

“It was a major milestone when SalMar bought the first facility, and when the fantastic Bluegreen team built it last year. It’s just fantastic to see happy salmon swimming around in Marine Donut.”

From left: Geir Andresen, Elg Thunes, Nils-Johan Tufte (all from Bluegreen), Johannes Schjølberg, Mykhaylo Ivashchenko, and Erlend Are Larsen (all from SalMar), at the first smolt stocking on Friday.

Geir Andresen has been responsible for the construction and handover of Marine Donut, which Bluegreen says is the world’s largest thermoplastic structure. Now, he has passed the baton and the responsibility for Marine Donut to Erlend Are Larsen, who is SalMar’s operations manager at the facility.

“The fish are calm and distributed well in the facility,” said Andresen. “Everything has been successful so far.”

Now that the fish are swimming around in the Donut, Tufte expects more orders.

“We have received incredible attention over the past year, and many fish farmers are interested. Both here in Norway, in Canada, Scotland, the Faroe Islands, and Chile. But everyone has wanted to wait to see how the fish thrive in the facility before signing. We believe there will be a new order soon,” he said.