Larve de barbeau fluviatile dans laquelle on distingue les otolithes
Barbel larva, Barbus barbus, 2 days after hatching, in which the otoliths – mineral concretions found in the inner ear of vertebrates – can be distinguished (in dark beige). Otoliths are different shapes depending on the species. It is possible to use them to estimate the age of a fish in days by counting the successive daily deposits of CaCO3 (calcium carbonate). After 200 days, it becomes difficult to estimate the age in days. Otoliths can also be used to work out an approximate hatching date, and thereby the length of the reproductive period of the species. Otoliths are also found in the digestive tracts of piscivorous fish. By analysing their shape, we can identify the species they came from and find out about the diets of these fish. Good understanding of the characteristics of the barbel life cycle helps research scientists target actions to promote the ecological restoration of this species. Indeed, the life cycle of the barbel, which is present in several areas of the Rhône, is affected by the numerous hydroelectric developments present.