Saumon (Salmo salar) d’Atlantique Nord-Ouest : Calibration Franco- Canadienne de l’estimation de l’âge. Rapport final du contrat SALMOCODAGE

France and Canada work together to follow the salmon populations (Salmo salar) of the North-western Atlantic, integrating the French territory of Saint Pierre and Miquelon (subdivision 3Ps). Ageing data are thus provided by these countries. The age estimation of salmon is carried out starting from the scales. These present two distinct areas because this migrating fish lives at first in rivers and the second part at sea with some passages in rivers (homing phenomenon). As a result of which, the interpretation of ages from these scales is difficult. The purpose of this meeting which was held in Saint-Pierre and Miquelon from the 10 to September 14, 2012 with French and Canadian scientists, was to measure and optimize the precision of the age data provided by these countries for the evaluations of these populations. Beforehand, 136 images of scales were interpreted. This first analysis showed a percentage of agreement between the scientists of 68% with a coefficient of variation of 11.6%. At this meeting, the images were observed making it possible to identify the sources of bias. They reside mainly in the first part of life of fish i.e. the life in river. Moreover, this meeting made it possible to show the difficulty of interpretation of images of scales. After writing a common protocol for both France and Canada, the second interpretation was carried out showing a percentage of agreement between the scientists of 80% with a coefficient of variation of 6.8%. Lastly, some images presenting total agreement, were annotated to begin a reference collection of salmon of the North-western Atlantic. This workshop showed the significance of calibrating the age interpretation, in particular those of salmon (Salmo salar) of the North-western Atlantic.