Refilling behaviour of Atlantic salmon (Salmo salar) in submerged sea cages with air-dome

Abstract

Production of Atlantic salmon in submerged sea cages may solve surface related challenges like sea lice and toxic algae blooms but previous trials have faced problems linked to buoyancy. Korsøen et al. (2012) showed that salmon adapt rapidly to refilling in air-dome, using plexi-glass (1m x 1m, with height of 0,3m), but not by normal refilling behaviour. This study suggests Atlantic salmon refill nearly singularly by rolling in an eight squared air-dome with diameter of 2,5m and height 0,1m during submergence. Leaping was also observed in the air-dome, but at a limited level. This study suggest that Atlantic salmon were able to maintain neutral buoyancy by refilling every other day in the air-dome, with swimming speeds ranging from 1,2 - 0,5 Bl s-1 throughout the experiment. This study also revealed that refilling activity in an air-dome varies diurnally, with numerous collinear factors as potential drivers for this. The activity in the air dome was observed using a camera attached to the inner side of the dome. Sixteen samples were made in the period from September 2019 – June 2020. Three steel cages of (12 m x 12 m x 15 m) with 6000-6500 salmon and one air dome per cage were used.