Within a month, the second, modified Aquatraz cage will be in place at MNH's Eiterfjord site. Photo: MNH.
Within a month, the second, modified Aquatraz cage will be in place at MNH's Eiterfjord site. Photo: MNH.

Aquatraz 2.0 to be delivered next month

Norwegian salmon farmer Midt-Norsk Havbruk (MNH) will take delivery of its second Aquatraz semi-closed cage next month, with two more due later in the year.


The first of the steel-walled cages was stocked with 180,000 fish with an average weight of just under 1.5kg in October. The fish were taken from standard net pens and were de-loused with fresh water before entering the Aquatraz.

Midt-Norsk Havbruk told Fish Farming Expert’s sister site, Kyst.no, that it had had good growth in the first stocking and is now in full swing with preparations for receiving cage No.2. 

Aquatraz factfile

  • The top eight metres of the Aquatraz comprise solid metal walls, helping prevent sea lice, which are largely found in the upper water layer, from entering the facility. The open panels at the lower level allow natural water flow in the event that the cage’s mechanical water supply should fail.
  • Water is pumped from depth into the cage, and is then circulated by another pump, ensuring an optimal environment for the fish in water that is rich in oxygen and maintains a more even temperature.
  • The fish are contained in a net pen inside the steel wall. The net can be lifted out of the water for maintenance and are disinfected through drying or freezing in the winter.

Test programme

Steingrim Holm, project manager and technical manager for the Aquatraz project, said the second cage is now being put together in the dry dock of the manufacturer, Fosen Yard.

“Launch is scheduled for week 6 in 2019 with delivery of the completed cage at the end of February 2019. Cage No.2 will mainly follow the same installation and test programme as cage No.1,” he said. 

Holm points out that the yard has made minor structural changes during the construction of cage No.2.

“And we’re installing four pumps on cage No.2. Experience so far shows that we get good water exchange with two pumps, but we want to increase the water flow rate in terms of trimming the salmon.”

Steingrim Holm: Extra pumps added to the second cage.
Steingrim Holm: Extra pumps added to the second cage.

The cage will be placed in the same grid as the first pilot in the Eiterfjord in Nærøy municipality in mid-Norway.

“We will put out fish in March 2019, and the number of fish will be just under 200,000,” said Holm, who pointed out that those involved have learned a lot from model tests, analyses, construction, installation and testing / operation, which they will utilise in the development of the next generation Aquatraz (cages 3 and 4).

“In addition, we are working on an extensive biological measuring program in the Aquatraz project, where we monitor fish health and fish welfare to compare how the Aquatraz cage performs. For the project to succeed, both technology and biology must work well together, so that we can produce top-quality salmon at a competitive price,” concluded Holm.