AKVA group ASA established ATLANTIS SUBSEA FARMING AS in collaboration with Sinkaberg-Hansen AS. The company has carried out large-scale development and testing of submersible salmon farms. After being granted a development permit, the company conducted extensive testing and documentation work from 2014 to 2021.

The project has now been completed and AKVA group ASA owns the rights to the technologies that were developed. Customers and other partners interested in Atlantis are requested to get in touch with the contact persons mentioned at the bottom of this page.

Experience from the project shows that fish behaviour and welfare was good and that the fish quickly learned to use the air dome to fill their swim bladders. The results show that it is entirely possible to avoid lice infestation in submerged cages provided that the fish are as free of lice as possible when exposed, the cage is brought to the surface as little as possible (requires the use of lice monitoring cameras) and that the entire locality has deep farming solutions.

Technical solutions

• The entire structure is lowered to below 20 m and only buoys are visible on the surface.
• A common frame mooring with enlarged surface bends
• The floating cage has no polystyrene and has an accompanying bottom ring
• The net is a regular nylon net with Lift Up for dead fish collection
• A net roof is "attached" to the floating cage and an air dome is attached to the middle of the net roof that provides the fish with air via an air pocket.
• It is fed with water in points around the air dome
• Separate remote control systems have been developed for raising and lowering cages, feeding and monitoring the facility

Atlantis is well suited for exposed sites, as there is little infrastructure on the surface once the cage is lowered down. This requires a barge that can withstand the environmental conditions at the site. Key features and structures are:

• Raising and lowering of pens: The pen (submersible) is filled with water when lowering and with air for raising. The pen goes obliquely into the water column and the raising and lowering process takes approximately 20-30 minutes. Raising and lowering of pens is controlled by AKVA group's control system, AKVA connect and can be done from the barge or remotely controlled from another location. This also applies to all other functions such as filling air in domes, monitoring of sensors on pens and air domes, camera surveillance, control of light, etc.
• Air dome at depth: Submersible fish farms are not a new invention – there are a number of facilities for different species. However, it has never been developed for salmon on the scale we have worked with here. The reasons for this are that salmon have an open swim bladder with a channel between the swim bladder and the oral cavity. They have a natural need to fill their swim bladders about once a day and in an open pen they swim up to the surface and "snap" some air. This is not possible in a submerged pen and the salmon must have access to an air pocket at depth. We do this via an air dome located at the top of the submerged cage.  (Figure x). The air is replenished every day using AKVA connect control system.

Picture: Filling swim bladder in the air dome.

Picture: Air dome in a raised position.

• Feeding at depth: The feed is mixed with water on the barge and then transported out to the cage and down to the air dome. The feed is distributed to the fish directly under the dome and this area is illuminated – so that the fish can see both the feed and the air pocket. The fish in Atlantis behaved no differently during feeding than the fish in the surface cages and there are no negative experiences with feeding in Atlantis cages in general.
• Camera and sensors: The fish are monitored by a camera fixed to a line under the dome. A louse monitoring camera approved by the Norwegian Food Safety Authority for lice counting is used for monitoring fish welfare and lice, as well as for counting lice. There is no need to take the cage to the surface to count lice manually.

Results and conclusions from Atlantis Subsea Farming – project

Atlantis Subsea Farming has been a close collaboration between SinkabergHansen, AKVA group and Egersund Net (now wholly owned by AKVA group), as well as external suppliers and partners.

"The companies have worked together on practical solutions that will work at sea. The goal is to separate salmon and lice through preventive work to avoid delousing operations and we have great faith in deep farming moving forward,"

says Svein Gustav Sinkaberg, President and CEO of SinkabergHansen.
(Source: iLaks 18/3-22. AKVA groups sells its shares in Atlantis Subsea Farming to SinkabergHansen).

Would you like to delve deeper into Atlantis-related matters? You can read more information and access all reports here.

Knowledge-based technology

In collaboration with Frode Oppedal and his research group at the Institute of Marine Research, systematic efforts have been made for several years to learn about fish behaviour related to the use of air domes and feeding in submerged cages. The research projects FÔRDOM and DypDom are funded by the Research Council of Norway, AKVA group, Egersund Net and Sinkaberg Hansen.  The results are directly relevant to the work with Atlantis.
Picture: Assessment of fish behaviour in the air dome at the Institute of Marine Research's facility at Matre by Frode Oppedal, IMR, and Hege Sekkenes, Val R&D

Atlantis has also carried out several tests in SINTEF Ocean's flume tank in Hirtshals, which have provided invaluable knowledge about how the overall structure behaves under different environmental conditions. SINTEF has also assisted in measuring forces in the plant at full scale in the sea.

Large-scale testing of the pilot cages has taken place at sites in the area around Rørvik in Nord-Trøndelag.

Main conclusions Atlantis - project

The main conclusions from the project are that fish behaviour and welfare was good and the fish quickly learned to use the air dome to fill their swim bladders. Feed factor, growth, mortality and harvest results show normal values compared to ordinary production, provided that adjustments are made for lower temperatures at greater depths. It resulted in the Atlantis cages only being deloused once compared with the surface cages in the facility, which were deloused three times. One delousing is assumed to be due to the fact that delousing of the surface cages results in the infestation of lice in the submerged cages through the transfer of lice via the water masses internally at the site. Experience indicates that it is entirely possible to avoid lice infestations. To successfully keep the fish free of lice, it is extremely important to:

• Release as many lice-free fish as possible throughout the facility
• Raise the cage as little as possible to the surface, which requires the use of automatic lice counting and monitoring of fish and technical solutions in the depths
• Use deep farming with all the cages on the site, whether it is Atlantis, Tubenet or another technological solution.

The latest results show that it is possible to avoid lice infestations in submerged cages provided that the fish are as free of lice as possible when released, the cage is raised to the surface as little as possible (requires the use of lice monitoring cameras) and that the entire locality has deep farming options, i.e., that the biomass is below 15-20 meters or deeper (depending on the locality). The challenges with salmon lice are greatly reduced by lowering the fish beneath the lice layer, but under certain conditions, for example by stirring in the water masses, one can still get an increase. In the event of an accident, Atlantis can be raised, the dome and roof removed and delousing can take place in the usual way.

Picture: Lice numbers counted with Aquabyte cameras in Atlantis 1, Atlantis 2, control 1 and control 2 from week 22 to 36. The lice figures are given as the average number of lice per fish per week, all lice stages combined. Blue stars mark where the control cages have undergone Slice treatment, red stars mark where the control cages have undergone non-drug treatment and green stars mark where all cages have undergone non-drug treatment.