Testing of an Archimedes pump for gentle and ethical handling of Atlantic salmon

In Atlantic salmon aquaculture, routine handling of fish is conducted during grow-out for e.g. sea lice treatments or vaccination as well as transfer to fish processing facilities at the end of the production cycle. This usually involves crowding the salmon in a small volume of the cage and subsequently pumping of the fish, which can trigger stress responses and cause injuries and mortality. The industry needs to develop new technologies and methodologies that include more gentle handling of the fish and thus improve salmon welfare. In this project, an Archimedes pump will be tested that is designed for gentle transfer of salmon up to 10 kg avoiding stress and welfare issues. The pump is built as a small-scale prototype that will be tested at the research facility of Nofima in Sunndalsøra on approx. 650 post-smolt salmon in total (approx. 200-300 g in size) in available outdoor tanks that allow the placement of the pump next to the tanks. The experiment consists of 1 pilot-test with approx. 100 fish each to ensure successful pumping of water and fish through the Archimedes pump. This allows to detect potential issues with the pump design that need to be improved before conducting further trials. During the main trial, approx. 250 post-smolt salmon will be transferred between tanks in two replicates and the biochemical and physiological response of the salmon will be tested 24 h before, as well as 1 h , 24 h and 48 h after the transfer. Moreover, fish will be hand-fed 24 h, 48h (and potentially 56 h) to observe when re-feeding occurs and monitored for behavioral responses and mortality. All trials will be conducted under controlled conditions and health and welfare of the salmon will be continuously monitored. The number of fish used in this experiment is kept to a minimum that is required considering individual variation in stress and welfare responses in this species. An additional testing for optimizing the method of fish entering the fish pump will be conducted with 300 post-smolt salmon in the same tank set-up as described above.