«We still need to develop innovative solutions in technology and biology if the results are to be seen in the agriculture statistics», says Bendik Fyhn Terjesen (photo: Terje Aamodt/Nofima).

Project Year 2014

Reduced losses with post-smolt

All farmed salmon might survive in future facilities for post-smolt production. The key is precise control over the salmon’s environment.

When salmon are stocked into open cages in the sea, they meet a changing environment, disease and sea lice. Many small salmon smolt are not robust enough to survive.

This is part of the problem that scientists and the aquaculture industry have been collaborating on solving for the last three years in the Optimised Post-smolt Production (OPP) project. They have been looking at how the time salmon spend in open cages in the sea can be reduced by increasing the time onshore or in closed-containment systems at sea. In present-day aquaculture, it is normal to transfer smolt from the freshwater system onshore to open cages at sea when they weigh about 80 grams. In OPP, the fish have been kept in an closed environment past this stage and right up to 1 kilo (post-smolt). The salmon are then transferred to traditional cages until they are of a suitable size for harvest at 4-5 kilos.

After a series of trials, Senior Scientist Bendik Fyhn Terjesen and colleagues obtained very good results with post-smolts with low salt concentration in the water, good exercise and careful handling in closed recirculation systems onshore until the salmon reached 600 grams.

The fish were then stocked into normal cages in the sea. When the salmon had reached 2.5 kilos, 99 per cent had survived. Other partners in OPP have found correspondingly high survival rates in semi-closed facilities at sea. According to figures from the Norwegian Food Safety Authority, the average survival rate for Norwegian farmed salmon in the marine phase is 84 per cent.

«These results show that some of the salmon find it too difficult when they are moved into the sea when young. But these become more robust and better able to stand the marine environment as young adults of well above 250 grams», says Fyhn Terjesen.

The OPP trials have shown that with good environmental control there is excellent potential for a high survival rate. But achieving a high survival rate over time in normal operation is more difficult than in trials. «We still need to develop innovative solutions in technology and biology if the results are to be seen in the aquaculture statistics», says Fyhn Terjesen. The results from OPP were presented at the «Smolt Production in the Future» 2014 conference, which Nofima and Sunndal Næringsselskap organise.

Marine Harvest, Grieg SeaFood, Smøla Klekkeri & Settefisk, Lerøy, Lingalaks, Erko Settefisk, Hauge Akva, UNI Research, University of Bergen, Norwegian University of Life Sciences, Bergen University College, NIVA and the National Veterinary Institute.

Research Council of Norway and an industry consortium. The Fishery and Aquaculture Industry Research Fund funds associated activities.

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