Are submerged cages in Atlantic salmon aquaculture feasible?
Most Atlantic salmon aquaculture industries around the world keep their stock in surface-based cages, which can face issues such as poor environmental conditions and the presence of parasites such as salmon lice. This has generated interest in submerging cages underwater to try and prevent parasite infestations and improve conditions for fish. A submerged cage was recently deployed by a salmon farm in China. However, there are several obstacles that must be overcome before submerged cages can be deployed. Submerged cages can have adverse effects on fish buoyancy, which can alter swimming speeds and cause tilted swimming at night time. This in turn can reduce growth and cause vertebral deformities. Researchers at the Institute of Marine Research and University of Melbourne compared submerged and surface-based farming of Atlantic salmon over 42 days, to determine if continuous light can help increase swimming speeds at night and prevent tilted swimming. They found using continuous light increased swimming speeds, reduced tilted swimming and spinal deformities. Salmon lice infestations were also reduced by 72%. However, salmon growth in submerged cages was 30% lower compared to surface cages. Therefore, developing and engineering technologies to allow salmon to refill their swim bladders in submerged cages at commercial scale is an important area of research that should be further researched before they can be deployed at larger scales. To read the article, click here.
An example of a submerged cage (Fish Farming Expert, 2017)