Aquaculture, News

Petroleum technology for ocean farming

Ocean Farming has plans to farm salmon in far offshore sites within the next years. Based on deep-water petroleum technology, the steel cage farms could produce eight times as traditional inshore farms.

Norwegian company Ocean Farming, a subsidiary of SalMar, has developed its ocean farm concept on similar technology used to anchor floating oil platforms to the seafloor. A circular steel structure with a grating covering the bottom and walls of the submerged part will be fixed to the seabed by eight catenary mooring lines. Flotation tanks placed beneath the six vertical main columns will support the whole construction.

The project draws upon the petroleum expertise of Gunnar Myrebøe, a former project leader for Statoil’s Snøhvit gas field in the Barents Sea, now project advisor for Ocean Farming. The company has also engaged Global Maritime, engineering specialists within the oil and gas maritime industry, for the technical design and engineering studies of the fish farm.

“The design combines the best of existing technology and solutions from the Norwegian fish farming industry and the offshore oil and gas sector,” said Arvid Hammernes, Ocean Farming chief executive.


The submerged facility is an anchored fixed structure that can float steady in exposed ocean at water depth of 100-300 meters, where the aqua biological conditions are more ideal for aquaculture on the “fish’s terms,” according to Hammernes. One of the main reasons for moving into more open free flowing waters is that the current here has a more steady direction compared to the typical tidewater found in the fjords that flows more back and forth.

“That means that you have a more constant replacement of the waters offshore than in the fjords,” said Hammernes. “You can also put a greater distance between each fish farm, reduce interaction between the facilities and reduce the footprint on the environment.”

All of the farming operations can be managed on board the facility without making use of service vessels and outside equipment. The fish can therefore stay inside the net from smolt stocking to harvestable fish. The facility is also equipped with one moveable and two fixed bulkheads that can divide the facility into three compartments enabling different fish operations to be performed. The facility is fully automated, avoiding heavier manual operations. During normal operation, a crew of 2–4 people will monitor and manage the facility.


Ocean farming uses steel cages that can potentially guarantee for less fish escapes than flexible inshore net pens. Some biologists even believe it could reduce exposure to salmon sea lice. But one of the other key drivers for going farther offshore is the lack of sufficient farming concessions near shore in Norway. The proposed cage would be 110 metres wide — twice the average diameter of inshore farms — and could hold eight times as much fish, according to Ivar Nygaard, project leader at SINTEF MARINTEK, which conducted test trials for Ocean Farming last year.

“It starts to get filled up in the locations inshore (Norway), so it is necessary to go out in offshore waters,” said Nygaard. “If we go offshore, you must think in terms of larger and stronger facilities. It’s more costly, but you can increase production 8-10 times.”

The Norwegian Ministry of Fisheries and Coastal Affairs issues aquaculture licenses for salmon, trout and rainbow trout through licensing rounds. They are limited in number and subject to a license fee. The maximum allowable biomass per license is 780 tons, except in the counties of Troms and Finnmark, which allows for 900 tons. There are also biomass limitations on the individual production sites.

Separately, the Ministry recently granted special licenses based on so-called green concessions, i.e. those that address sustainability issues such as sea lice and escapes. In the future, the ministry aims at opening up for increased sustainable production through a new zoning policy that could allow for higher output in certain areas. The proposal is part of the White Paper on sustainable aquaculture being put forward to Parliament this spring.


MARINTEK has already tested the steel cage structure for the expected motion behaviour out in Frøhavet offshore mid Norway, one of the possible locations for the new farm concept. Model tests performed last year in its Ocean Basin at Tyholt, Trondheim exposed the structure to maximum single waves of up to almost 10 meters. The results showed that the structure could withstand expected loads in the 150-meter waters. If the project proceeds as planned, Ocean Farming’s concept could be the first of its kind.

“To my knowledge, there are no similar projects with that size and structure anywhere in the world,” said Nygaard.

Separately, Norway is studying the possibility of cultivating salmon in more exposed sites farther offshore through the SINTEF research project SustainFarmEx (Towards Sustainable Fish Farming at Exposed Marine Sites). Set to conclude by June 2015, the four-year study aims to determine operational limitations for equipment, operations and people, define dimensional limitations and establish design criteria, and solve key bottlenecks connected to fish farming in more exposed sites.

The five work packages have focused on sustaining exposed farming operations, human safety and performance; reliable fish farm structures; remote surveillance and controls; fish transfer and boat to barge unload; and economic, value chain optimization. SINTEF Fisheries and Aquaculture and SINTEF Technology and Society were research partners with the Norwegian University of Science and Technology NTNU, Aquaculture Research Station of the Faeroes. The Norwegian industry partners include Egersund Net, Mørenot, Eidsvaag, ACE (AquaCulture Engineering), Luna, Selstad, Lerøy Seafood Group, Aanderaa and Akva Group.

SINTEF Fisheries and Aquaculture also recently concluded project Exposed Salmon Farming in High Currents and Waves (Exposed Farming) in 2013. The three-year study included partners Institute for Marine Research, Bodø University College’s Faculty of Biosciences and Aquaculture, Fiskeaaling Aquaculture Research Station of the Faeroes, Salmar, and Bakkafrost (Faroe Islands).

Read more articles from Norwegian aquaculture and fisheries in:

Norway Exports Seafood, Fishing & Aquaculture.