Aquatraz development project

Aquatraz development project

- semi closed fish cage protects against salmon lice and escape

In April 2017, Midt-Norsk Havbruk (MNH) received four development permits to develop the Aquatraz – the escape proof semi-closed steel fish cage, protecting against sea lice and escape. This has been an exaciting, and thus far successful development project. The first Aquatraz fish cage was launched in August 2018. Merely two years later, the fourth fish cage has been launched, totalling three development generations. During this period, the Aquatraz fish cages have accumulated three years operating time and has produced 5,000 tonnes of salmon. The fourth generation Aquatraz will also be available to selected fish farmers whom have not been part of the development project thus far. 

The technology development has progressed much faster than what we envisioned at the beginning of the project. This would not have been possible without close and good cooperation between Aquatraz, Fosen Yard and Midt-Norsk Havbruk, says Steingrim Holm, project manager at Midt-Norsk Havbruk.

No escape, deep lice skirts, excellent water flow


Safeguarding against escape and abundant water supply facilitates a substantial increase in fish density inside the fish cage.


Aquatraz fish cages have a water flow system that ensures a changeout of the water volume every 12-15. min. Mixers create a flow inside the cage, causing water to be pulled up into the fish cage from depths free form sea lice and algae. The water flow system also exercises the fish. The intensity can be adjusted to accommodate fish size.


The Aquatraz cages have non-permeable lice skirts and for the first three cages, G1-G2, these were 8 meter deep. Aquatraz G3 has increased the lice skirt depth to 18 meter. The upcoming Aquatraz G4 is planned with 25 meter deep walls / lice skirts in steel. 

Flexibility, efficiency and safety in operations


Aquatraz G1-G3 deploys a gentle method for delivering fish that involves the lufting system. The G4 will have a new system for vertical sectioning that allows for sorting fish, starving and delivering fish in batches, without lifting the cage. The salmon are delivered from the bottom of the cage, utilizing its instincts to swim downwards, and causing the salmon less stress.


The lifting system can elevate the entire fish cage out of water, providing easy access for washing, disinfecting and maintance of the cage on site. The G4 will include automatic removal of fouling from the inside wall.

Aquatraz 1 & 2 - G1

- semi closed steel fish cage

The first Aquatraz was launched, towed to the Eiterfjorden and filled with salmon in October 2018.

Cage number one, which was in place in October, has worked better than expected, both in terms of biology and technology. In addition, it provides significantly better working conditions than traditional cages,
mr. Holm explains.

Shortly after, the second cage followed. In April 2019, fish were swimming in both Aquatraz # 1 & # 2.

In May 2019, Aquatraz’s unique fish delivery solution was tested for the first time. The operation proceeded as expected.

By taking out the fish from the bottom of the cage, there is no need for as much urgency and pressure on the fish. The salmon remained calm during the entire loading, so this project is good for fish welfare,” said Roger Eiternes, production manager in Midt-Norsk Havbruk.

-This is a dream for EHS (environment, health, and safety). Today we have not used a muscle to raise the cage, Eiternes continues.

– Aquatraz # 1 & # 2 were moored on site along traditional cages for comparison. The sea lice exposure in the reference cages was significantly greater. Few of the salmon in the Aquatraz cages had sea lice, and no delousing was necessary, mr Holm explains.

Aquatraz 3 - G2

- safeguarding your fish from sea lice and escape

October 2019, the third Aquatraz fish cage was launched, the first of the second design generation. 
–  We have brought with us all experiences from the fabrication, design and operational operation of the first two cages,” said Steingrim Holm.

Aquatraz G2 Photo Steinar Johansen


Access was improved as the horisontal spokes were removed.


The walkway is considerably wider, 9 feet, and includes space for 10 foot containers providing dry  storage space for the generator and electricity cabinet, amongst other.


A new electric lifting system that allows lifting and lowering without relying on energy supply from a boat.


The fish cage became more manufacturing-friendly than its predecessor.

Aquatraz 4 - G3

- with deeper sea lice skirts

– The depth of the closed part of cage is increased from eight metres to 18m by fitting a lice skirt in the window panels, Holm said (

The lice skirt extension consists of non permeable tarpaulin implemented in the side panels of the cage. Tarpaulin has also been implemented at the bottom of the cage, extending three meters from each side along the bottom net. Overall, these changes contribute to improved internal water circulation and an increase of the water intake from further water depths. This will improve fish health and further reduce the problem with lice. 

– So far, the operation of the Aquatraz cage in Årsetfjorden has worked very well. Both temperature and salinity measurements show that we’re taking in water from a depth of about 20 metres, which is good with regard to sea lice pressure,” Holm explaines (

The number of sea lice in G3 is low and decreasing (without any treatment)

Aquatraz G3. Photo Steinar Johansen/MNH

Aquatraz G4

- 22,5 meter steel lice skirts, sorting and delivery in batches

The fourth generation Aquatraz has the latest improvements refined in the fall of 2020. Where G3 got the lice skirts extended with use of tarpaulin, the G4 is planned with 25 meter lice skirt in steel. The side panels (5 m) and bottom will be steel/grp grating, further escape proofing the fish cage.

Sandstad revealed to
– Unlike previous generations, G4 can divide the farming volume into adjustable sections, like pieces of cake. This enables the delivery of fish without raising the cage. The division also provides opportunities for sorting fish as well as batch starvation and delivery of fish. During the work with G4, it has also been important to focus on operations. In the first generations, the main focus was on the fish, but for G4, which is to be a commercial cage, it is important that everything is automated in most operations. Therefore, greater flexibility in production has had increased focus.