Guide to scale interpretation and age estimation for Atlantic Salmon (Salmo salar) from French populations
Initial work carried out in 1985 provided a guide for interpreting the scales and estimating the age of the Atlantic Salmon (Salmo salar) from French populations. But, for more than 30 years, the demographic structures of populations and the life history strategies of the species have been modified due to high variability of life conditions in freshwater and the sea because of global change. In fact, the objective of this new guide is to confirm the size-age keys of current French salmon populations and to summarise all the difficulties currently encountered for interpreting scales using, in particular, the capture-mark-recapture monitoring operations performed on some rivers. The species is still naturally present in numerous French rivers, especially in Brittany, Normandy and the Basque Country. After a presentation of current knowledge on the ecology and life history strategies of the salmon in France, the structure of its scales and the methods for collecting, preparing and mounting them are briefly described. The definitions of the scale structures and the standard age notation system are respecified, referring to the propositions already made in the scale-reading guides for the Salmo genus. This new guide is richly illustrated with examples of salmon scales from different regions showing the typical structures observed. Finally, the main difficulties encountered for estimating the age are analysed by means of examples, with proposed possible solutions and recommendations.
Auteurs du document :
BAGLINIERE J.-L., JEANNOT N., NEVOUX M., LAMIREAU L., LANGE F., JOSSET Q., MARCHAND F.