Skånsom behandling av lakselus og AGD med bruk av avsaltet sjøvann i merd

Non-medical treatment is a future oriented and gentle method for battling ectoparasites on farmed salmon, and freshwater has proven to have good effect on both salmon lice and AGD. At the present, freshwater treatment is done either in closed tarpaulins or in wellboats. The long-lasting treatment process prevents feeding and growth. The innovative idea is to form a semi closed treatment area, containing reverse osmosis produced freshwater, inside the cage that the fish can access through an open gate. Fish that visit the freshwater body regularly treat themselves, which eliminates the need of handling the fish. This concept is inspired by the natural treatment effect experienced by wild salmon that migrates up rivers to spawn. To summarise, the innovation consists of new technology and new methods that all together makes up a new type of gentle treatment system for sea lice and AGD. Methods for "voluntary behavioural manipulation" of fish will be investigated to be able to control the treatment. This can be achieved by exploiting their preference for environmental variables such as light, temperature and access to feed. Experiments in small and large scale are ongoing. Different salinities are being tested as well. The desalination process does not change the water temperature, which makes it possible to produce freshwater with a favourable temperature by accessing intake water from different depths. A depth-adjustable seawater intake for the desalination system is therefore developed. It is important to keep the freshwater in the cage free of seawater contamination. However, the fish must have free access to the freshwater volume and the system cannot prevent cage management. Three flexible structure concepts were developed and exposed to different sea states in model experiments with currents and waves at Dora, Trondheim. The measurements are analysed and presented (Report May 2019). A full-scale trial of the system has been tested at a commercial facility (Mowi's farm at Haverøy, Sotra)during autumn 2017 - autumn 2018, where water quality parameters as well as the fish's movements have been monitored. The water quality assessments, emphasizing salinity within the freshwater supplied enclosures, were reported Nov. 2018. It seemed difficult to maintain a stable fresh water/brackish water layer to a depth of 3 m with the applied enclosure design. Use of echo sounders during 20 days in Oct. 2018 indicated lower abundance of fish within the enclosures compared with the surrounding cage volume (Report CageEye, Nov. 2018). However, the fish abundance increased over the short test period implying the need of long-term tests to verify this trend.

Å utvikle et merdbasert behandlingssystem med bruk av avsaltet sjøvann, som gjennom en full produksjonssyklus, evner i vesentlig grad å begrense luseprevalens og -intensitet, samt problemer med AGD-smitte.

Ideen i prosjektet er å benytte avsaltet sjøvann i avgrensede (øvre) deler av oppdrettsmerder, som laksen manipuleres til å oppholde seg i, slik at problemer med amøbegjellesykdom (AGD) og lakselus blir kraftig redusert. For å få kontroll over hvor mye laksen benytter behandlingsenheten, vil vi bruke "frivillig styring" ved å utnytte laksens preferanser for omgivelser når det gjelder lys, temperatur og tilgang på fôr. Prosjektet vil utvikle 1) Innsug for henting av vann på ulike dyp, 2) Teknisk løsning på behandlingsenhet, og 3) Manipuleringsmetoder for styring av laksens posisjon.