Aquatraz development project

In April 2017, Midt-Norsk Havbruk (MNH) received four development permits to develop the Aquatraz – the escape proof semi-closed steel cage. This has been an exciting, and thus far successful development project. The first cage was launched in August 2018. Merely two years later, the fourth cage has been launched, totalling three development generations. During this period, the Aquatraz cages have accumulated three years operating time and has produced 5,000 tonnes of salmon. The fourth generation Aquatraz will be available to fish farmers whom have not been part of the development project. Construction will start in late autumn 2020.

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.


Safeguarding against escape and secured sufficient water supply have resulted in dispensation from the authorities to increase the fish density from 25 kg/m3 to 45 kg/m3 and to increase the maximum number of fish from 200,000 to 400,000 fish per cage.


Aquatraz cages have added circulating water stream that exercises the fish. In addition, the water supply system ensures that fresh water is obtained from lice-free water depths. The water exchange rate is 3600 m3/min.


The Aquatraz cages have non-permeable lice skirts and for the first three cages these were 8 meter deep. Aquatraz G3 has increased the lice skirt depth to 18 meter. The upcoming Aquatraz G4 will have even deeper lice skirts.


Aquatraz deploys a gentle method for delivering fish. While the lifting system lifts the cage the volume within diminish and the salmon follows its natural instinct and swims downwards, where it is pumped into a well boat from a fixed outlet point at the bottom of the cage. 


Besides facilitating gentle delivery of fish, the lifting system provides easy access for washing, disinfecting and maintance of the cage on site.

Aquatraz #1 & #2 - G1

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 lice exposure in the reference cages was significantly greater. Few of the salmon in the Aquatraz cages had lice, and no de-licing was necessary, mr Holm explains.

Aquatraz #3 - G2

October 2019, the third Aquatraz 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 Safeguarding your fish
Foto over og øverst: Steinar Johansen/MNH

Access was improved as the horisontal spokes were removed.


The walkway is considerably wider, including space for 10 foot containers which provide storage space and dry space for the generator and electricity cabinet.


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

The cage became more manufacturing-friendly than its predecessor.

Aquatraz #4 - G3

Aquatraz G3 with 18 meter lice skirt.

– 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 first two generations, Aquatraz G1 and G2, have performed very well technically. The biological results have also been good, with a reduction in lice spread compared to conventional cages with lice skirts. With the new G3 we take a huge step further in terms of protection against lice, says Steingrim Holm.

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. 

Aquatraz G4


The fourth generation Aquatraz G4 is currently on the drawing board where the latest improvements are being refined. Where G3 got the lice skirt extended with use of tarpaulin, the G4 will have even longer lice skirt in steel.

In May 2020 the Aquatraz G3 will be stocked with salmon. We expect to document the good effects of deeper skirts and improved water exchange during the summer. The results from G3 will then be included in the final phase of design for the fourth and last generation Aquatraz, Alf Reidar Sandstad, explains.