Grieg Seafood, one of the world's largest salmon producers, has shown that Atlantic salmon can be grown on land to harvest size with good biological performance, but also that, at the current scale and cost structure, the economics do not add up.

The company has therefore decided to dedicate all four production halls at Årdal Aqua exclusively to post-smolt production.

The trial saw a batch of salmon grown on land to an average weight of more than 5 kg before being transferred briefly to sea for purging ahead of harvest.

A total of 610 tonnes GWT were ultimately harvested, with low mortality and 95% of the fish classified as Superior quality. Grieg also reported no significant slowdown in growth at higher fish weights.

The decision not to continue growing salmon to harvest size, because production costs are higher than in conventional sea cages, shifts the focus back to post-smolt, where Grieg currently sees greater value from RAS.

Årdal Aqua has an annual production capacity of approximately 6,000 tonnes and, under the new configuration, Grieg will increase its total land-based smolt and post-smolt capacity to around 9,000 tonnes.

The Årdal experience therefore adds an important conclusion to the debate around RAS salmon: reaching harvest size on land can be technically viable without yet being economically competitive.

Grieg does not rule out the possibility that greater scale could change that equation, but for now considers it more profitable to use RAS to produce larger post-smolt and complete the grow-out phase at sea.