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Helping Salmon Cope with Stress of Transfer to Sea

26 January 2015

Scientists are keen to sort farmed salmon and provide them with exercise right from the early stages of their growth, in order to equip them to deal with the stress of transfer to the sea.

The aquaculture industry has faced persistent challenges relating to survival after the smolts have been transferred to the sea. Figures from the Norwegian Food Safety Authority show that the annual loss is approximately 16 per cent.

A significant part of this is due to fish in poor condition, which are more receptive for disease. Such fish die relatively soon after being transferred to the sea.

Nofima is attempting to achieve higher survival by the use of exercise and better sorting of salmon.

“The FitSmolt project is intended to discover how the smolt can develop higher resistance to disease, how we can get them to deal with various types of stress better, and how they can grow rapidly, with natural organ development,” said Nofima Senior Scientist Harald Takle.

The Fitsmolt project is co-funded by the Norwegian Research Council and the Norwegian Seafood Research Fund (FHF).

Sorting by swimming ability

The scientists have previously shown that sorting the young salmon by swimming ability gives postsmolts whose heart muscle is 24 per cent more powerful and whose gill surface area is 16 per cent larger. These fish swim 66 per cent more efficiently. The increase in heart capacity means that the fish grow more rapidly, and have higher resistance to disease.

The next stage involves exercising the salmon right from an early age until they are transferred to the sea, with swimming exercise at the correct flow rate. Previous results have shown that more salmon survive after transfer to the sea when they have undergone extensive exercise as smolts.

The scientists now want to see whether even more robust fish can be developed by exercising the fish throughout the complete fresh-water phase.

The exercise means that the fish develop significantly higher swimming capacity and heart strength, and this is why the scientists believe that exercise gives better survival.

“We also want to compare the heart capacity of farmed smolts with that of wild smolts, and identify markers that reflect these differences. The wild salmon will be taken from the Lærdal River, since we know that smolts from here are strong and swim well. The long-term goal is to ensure that future generations of farmed fish are at least as robust as their wild cousins,” said Mr Takle.

January 2015

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