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Add To Calendar 25/02/2016 14:00:0025/02/2016 14:20:00America/ChicagoAquaculture 2016SEMI-CLOSED SEA SYSTEMS FOR POSTSMOLT ATLANTIC SALMON Versailles 3The World Aquaculture Societyjohnc@was.orgfalseanrl65yqlzh3g1q0dme13067DD/MM/YYYY


S. Calabrese*,  B. Sævareid, O. Breck, R. Joensen, T.O. Nilsen, J. Kolarevic, S. Fivelstad, H. Takle, C. Hosfeld, L.O.E. Ebbesson,  S. Stefansson, B.F. Terjesen and S.O. Handeland
Department of Biology, High Technology Centre, University of Bergen, N-5020 and Marine Harvest Norway, Bergen N-5835

For the development of commercial scale semi-closed sea systems for postsmolt Atlantic salmon further knowledge is required on the biological limits for fish density and specific water flow. This was established in a small-scale laboratory setting. Knowledge gained was used to develop and test an industrial scale semi-closed prototype.

Fish density and specific water flow for postsmolts: Postsmolts 115.0 g ±13.6 g were stocked in 5 different densities (25, 50, 75, 100 and 125 kg/m3) with a specific water flow of 0.6 l kg-1min-1 or in 4 different specific water flows (0.5, 0.4, 0.3, 0.2 l kg-1min-1) with a set density of 75kg/m3. Effects on performance, physiology, external welfare (cataract, operculum, fin and skin damage) and skin health were assessed throughout the 8 week experiment.

Industrial scale semi-closed sea system pilot test: The semi-closed prototype tested is situated in Molnessund in the south-western part of Norway and has a volume of 21 000 m3. Atlantic salmon smolts (n=200 000, ~118 g) were transferred to the prototype in November and the study lasted for 6 months until fish were ~1 kg. Water quality, growth and survival were monitored and logged daily. Effects on external welfare and health were assessed before transfer and after 1, 3 and 6 months in the prototype.

The small scale study revealed that fish densities of 100 kg/m3 and above had a negative effect on postsmolt performance, physiology and external welfare (cataract prevalence and fin damage). Reducing specific waterflow below 0.4 l kg-1min-1 induced a typical physiological regulatory response seen with increased water CO2 and had negative effects on skin cell morphology. However, no negative effects were observed on macroscopic external welfare or growth. The industrial scale test of the semi-closed prototype revealed good growth and FCR (1.0) throughout the period. There were no observed effects of the prototype on external welfare indicators and water quality parameters stayed within recommended values. The survival was over 99 % the first 6 months in the prototype.

These studies show that if fish density and specific water flow are maintained at optimal levels, there is potential for good growth, welfare and high survival in semi-closed sea systems. The knowledge gained in these studies will further be used for optimizing biological conditions for postsmolts in semi-closed rearing systems.

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