Farm got rid of salmon lice - then new problems appeared

During a presentation at an event organised by the Stiim Aqua Cluster, Tormod H Skålsvik from Nova Sea shared his experiences with snorkel cages in aquaculture, reports Fish Farming Expert's Norwegian sister site, Kyst.no. He highlighted several positive aspects of the technology, but also emphasised that there is still work to be done to solve some challenges related to fish welfare.

Snorkel cages keep fish below the sea lice layer – approximately the top 10 metres of the water – so that they encounter fewer lice. When fish head up to the surface to fill their swim bladders with air, they are protected by a tarpaulin which encircles a wide tube in the middle, all the way up to the water line.

"We tested snorkel cages for the first time in 2022 at the Rendalsvik site," explained Skålsvik. He pointed to promising results regarding sea lice, with minimal occurrence throughout the entire production cycle.

No delousing

The results from the snorkel cages were compared with five other locations, and the lice numbers showed significantly lower levels in the snorkel cages. Skålsvik noted that they did not need to carry out delousing during the cycle, which he called "very promising".

The same is shown by the figures from last year at the same location. Despite the fact that the aquaculture industry in Northern Norway struggled with very high lice numbers during the summer, the lice numbers remained low at the site with the snorkel cage.

Welfare challenges

Even though the snorkel cages show good results in lice control, Skålsvik said that the technology still has its challenges.

"We experienced some welfare issues, including 'neck bending' in some fish. Although it was not a large occurrence, it is a clear indication that something is wrong," he said.

Other challenges included fish with water in the swim bladder and instances where the fish swam at an angle. Skålsvik explained that these problems are likely related to buoyancy and pressure conditions in the cages.

"The swim bladder is compressed by the pressure the deeper the fish stays, which can create buoyancy problems," he elaborated.

Disappointed with flexibility scheme

To address these challenges, further development of the technology is necessary, according to Skålsvik. Nova Sea has also embarked on other types of cage solutions.

In May, Nova Sea entered into a partnership agreement with FishGlobe, which develops closed farming systems. They are now set to build FishGlobe 30K, the largest variant of the system, and have taken over two development permits related to the project.

Regarding closed facilities and environmental technology, Nova Sea is disappointed with the environmental flexibility scheme that was sent for consultation before Christmas. As proposed, it only applies to areas that have had biomass limits reduced after being designated as red under the government's salmonid farming traffic light system, which aims to protect wild smolts from sea lice. Nova Sea believes this is too passive. 

Net must be cast wider

"It is important to work broadly and with many different actors to solve the challenges we face. A mix of technology and adaptation is the way forward,"  Skålsvik tells Kyst.no

He emphasises that although the snorkel cages show promising results, it is important not to exclude other technologies such as submersible cages, closed facilities and conventional cages. Submersible cages also keep salmon below the lice layer, but have an air dome below the surface to enable fish to fill their swim bladders, instead of a protected route to the surface.

"We believe in a future where conventional cages still have a role, but we must adapt and use new technology and methods to ensure sustainable development for the benefit of the fish and the environment," he concludes.