Introduction
Parts of future increased production of Atlantic salmon ( Salmo salar ) may take place in offshore environments. Companies have sketched several potential technological solutions to be put out in the open, harsh, oceans with a range of connected service management tools. Within Norway, politicians are positive and l egislation authorities have been steered to develop new regulations and review areas for offshore farming .
But will the salmon cope in offshore farming installation ? What are the biological challenges for Atlantic salmon in offshore compared to less exposed cages? And do we have enough knowledge to produce salmon offshore? Can new farming technology be based on biological premises?
Materials and Methods
Over the last decades several projects have addressed biological challenges to the salmon in exposed farming and a review was presented by Hvas et al (2021). Since then, more sophisticated trial setups in swim tunnels, observations in the field , development of new tag technology and farming methods have been carried out together with variable advisory reports. This presentation will show and summarize some key recent findings.
Results and discussion
Atlantic salmon is an athletic fish species with a surprisingly high s ustained swimming capacity that last for >72 hours at 80% of Ucrit (critical swimming speed). In fluctuating water speeds mimicking wavy conditions, salmon unexpectedly display higher swimming capacities compared to constant speeds . Fasting seem to have negligible negative effects on swimming capacity and periods of non-available feed may not become problematic. From observations within a limited number of cages, salmon display deeper swimming during strong surface wave actions. Submerged farming technology with airdomes for swim bladder filling may be a future successful offshore technology. Three offshore areas for farming outside Norway is being reviewed based on distance from shore, wave and current characteristics, temperatures, pathogen spread, bottom characteristics, wildlife and other conflicting interests together with fish health and welfare. Typically, offshore installations are large and most sketched future farming technologies are longer and involves 5-10× the number of salmon per cage compared to present farming. It is debatably how large offshore cages can become and still provide adequate environmental conditions for the fish. Even in present cage technology low oxygen conditions are regularly seen. F or some of the sketched enormous offshore cages, hypoxia might become a future challenge for the well-being of the fish . Offshore cage farming needs to be based on biological premises.
References
Hvas, M., Folkedal, O., Oppedal, F., 2021. Fish welfare in offshore salmon aquaculture. Reviews in Aquaculture 13, 836-852.