Age estimation

Method

Material

Binocular and PC with image capture and processing software.

Technic

1. Identification of the nucleus. The nucleus corresponds to the otolith of glass eel. It is generally the darker disk which includes in its center the primordium. Take a measure of the central zone. If the ring measures between 300 and 380 microns, it is the nucleus. The limit of the nucleus is the origin of the continental age, defined as age 1.

2. Count the annuli from age 1 to the edge of the otolith.

3. Make a virtual line along the largest growth axis between the primordium and the edge of the otolith.

4. On this line record the absciss of each age annuli.

5. Store the data in the form of a series of abciss for each sample.