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© Xavier COLOMBET/LEHNA/CNRS Photothèque

Coupe d'otolithe prélevé sur un chevesne



Max. size

21.67 x 16.26 cm / 300 dpi


Otolith section being sanded. It is still too thick to be able to see the nucleus. This otolith was taken from a chub, Squalius cephalus, a very common species of freshwater fish in Europe, and is viewed using an optical microscope. Otoliths are mineral concretions found in the inner ear of vertebrates. This one was taken from a fish caught during electrofishing as part of a study on the growth of larvae and juveniles in the abandoned channels of the Rhône. The aim is to estimate the age of the fish in days by counting the successive daily deposits of CaCO3 (calcium carbonate) on the otolith. Sanding involves polishing the otolith in order to reach the nucleus. This makes it possible to see the marks for each day from the nucleus to the edge of the otolith, along its longest axis.

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