Salmon mortalities average 16.3 per cent at sea

These were the most important findings in a nationwide survey covering the generations of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) transferred to sea in the autumn of 2010, spring of 2011 and autumn of 2011. The survey was carried out retrospectively after the stocks were harvested and the end point biological data were available.

Approximately 80% of fish transferred to sea were included in the survey. The registered losses for salmon were 16.3% and for rainbow trout 18.3 %. Average calculated non-registered losses varied from 1.3%-2.3% for the entire generations. A few dominating single factors responsible for the registered losses were pinpointed, although substantial geographical differences for the causes of specific registered loss were seen. Finnmark had highest losses, while Nordland had the lowest.

Large variations between groups of fish and sites were also recorded. A small fraction of the groups of fish were found to increase the average registered losses considerably. If the top fifth of the groups of fish with the highest registered losses were omitted from the calculations, the national average for the loss of fish in generations comprised by this study would be reduced by an estimated 5.3%.

The project was managed by Mattilsynet (the Norwegian Food Safety Authority) and financed by The Norwegian Seafood Research Fund (FHF). The statistical analysis were carried out by the Norwegian University of Life Sciences.