Atlantis Subsea Farming has completed two releases in its submersible cage. Photo: AKVA group.

‘Normal growth and good welfare’ for salmon kept 30m deep for 15 weeks

Salmon stocked in the Atlantis submersible cage in Norway have shown normal growth and good health, according to project manager Trude Olafsen.

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The cage has been developed by Atlantis Subsea Farming, a collaborative project between AKVA group, Sinkaberg-Hansen and Egersund Net.

Around 100,000 fish were stocked in Atlantis on February 18 last year. Atlantis Subsea Farming harvested 25,000 fish in late April and the rest in early June. The immersion periods amounted to 112 and 61 days, respectively.

Trude Olafsen: Has gained "even greater faith" in submersible cages.

A good alternative

Fish were originally due to be set out in the cage in November 2019, but due to unforeseen events combined with bad weather the stocking had to be delayed until February 2020.  

“We have now carried out two releases in Atlantis and the results indicate that the fish have a normal growth and good welfare, and this is of course incredibly important,” Olafsen told Norsk Fiskeoppdrett (Norwegian Fish Farmer) magazine.

“After stocking number two we have gained even greater faith that submersible cages can be a good alternative in some, more exposed localities in the outer coastal areas.

“The fish seem to get used quickly to living in a cage that is lowered to 30-40 metres, and biology is after all the most important thing here. Technically, Atlantis also works well, although of course we have some work left before everything works optimally.”

The Atlantic cage includes an air dome which allows fish to refill their swim bladders when the cage is submerged.

Air dome

Olafsen said the company was very interested to learn whether all the fish that were released in the second stocking would learn to swallow air in the air dome that is mounted in the roof of the cage to allow fish to fill their swim bladders.

“All our records of swimming patterns and feeding behaviour indicate that that happened. This is perhaps the most important experience we had during the stocking,” she says.

Atlantis Subsea Farming is carrying out three consecutive stockings of fish to ensure that the technology works well and that the welfare, well-being and growth of the fish are safeguarded.

Operation of submersible facilities will be explored further and the project should provide both many answers and new issues that must be solved. The goal is to develop technology with an investment framework that makes it possible to diversify the technology along the Norwegian coastline and in other parts of the world.