Trial shows salmon happy in submersible pen

Atlantis Subsea Farming – a collaboration between fish farmer SinkabergHansen, supplier AKVA group and net maker Egersund Net – stocked the pen in February with 100,000 fish weighing around 3kg each.

It was the first time such a large biomass, close to a full-scale operation, was tested in the structure, which was submerged 30m at its site south of Rørvik, in Trøndelag county. The first trial of the new cage took place last year.

Project manager Trude Olafsen said the growth had been good and the fish learned to use the airdome, which had been unstable in earlier trials.

‘We are very pleased with the results so far. The fish quickly calmed down and resumed a good pattern of movement inside the pen,’ said Olafsen in a press release issued by AKVA.

Surveillance

‘Close surveillance of the fish revealed normal behaviour and feeding pattern throughout the whole period.

‘The growth was about the same compared to ordinary pens at the site. The conclusion is that the fish learned to use the airdome in order to fill the swim bladder sufficiently and that the fish welfare was good.’

The salmon were treated for lice before being transferred to the pen, which was then deloused once during the production period. 

‘During the test period, the lice's life cycle and development in Atlantis did not differ significantly from what we know as normal/expected development in traditional surface pens,’ said Olafsen.

‘The results indicate that some larvae reach their infectious stage in the depth. Occurrences of deep-going lice have also been registered in other sites but at a lesser extent than in traditional surface pens.’

The first batch of 25,000 fish was harvested in April and the rest came out of the water in June.