Studie of the otolithes to estimate fish age

Rays of the anal fin of a barbel, Barbus barbus. This image shows the structure of the fin: its segmentation and the presence of three spines on the leading edge followed by branched soft rays. Laboratory experiments on the barbel help improve understanding of the characteristics of its life cycle, notably the crucial stages of its development. In particular, research scientists can study its growth thanks to otoliths. They can then target actions to promote the ecological restoration of this…

Rays of the caudal fin of a barbel, Barbus barbus. This image shows the structure of the fin, notably its segmentation. Laboratory experiments on the barbel help improve understanding of the characteristics of its life cycle, notably the crucial stages of its development. In particular, research scientists can study its growth thanks to otoliths. They can then target actions to promote the ecological restoration of this species. Indeed, the barbel is a species characteristic of several areas of…

Juvenile barbel, Barbus barbus, 28 days after hatching. Laboratory experiments on the barbel help improve understanding of the characteristics of its life cycle, notably the crucial stages of its development. In particular, research scientists can study its growth thanks to otoliths. They can then target actions to promote the ecological restoration of this species. Indeed, the barbel is a species characteristic of several areas of the Rhône whose life cycle is affected by the numerous…

Frontal section of a lapillus, a type of otolith taken from a juvenile chub, Squalius cephalus, a very common species of freshwater fish in Europe, 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…

Frontal section of a lapillus, a type of otolith taken from a chub, Squalius cephalus, a very common species of freshwater fish in Europe, viewed using an optical microscope (70x). 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…

Frontal section of a lapillus, a type of otolith taken from a juvenile chub, Squalius cephalus, a very common species of freshwater fish in Europe, 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…

Sagittal section of a lapillus, a type of otolith taken from a juvenile chub, Squalius cephalus, a very common species of freshwater fish in Europe, 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…

Barbel larva, Barbus barbus, 12 days after hatching. Laboratory experiments on the barbel help improve understanding of the characteristics of its life cycle, notably the crucial stages of its development. In particular, research scientists can study its growth thanks to otoliths. They can then target actions to promote the ecological restoration of this species. Indeed, the barbel is a species characteristic of several areas of the Rhône whose life cycle is affected by the numerous…

Barbel larva, Barbus barbus, 9 days after hatching. Laboratory experiments on the barbel help improve understanding of the characteristics of its life cycle, notably the crucial stages of its development. In particular, research scientists can study its growth thanks to otoliths. They can then target actions to promote the ecological restoration of this species. Indeed, the barbel is a species characteristic of several areas of the Rhône whose life cycle is affected by the numerous…

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…

Prepared otolith from a chub, Squalius cephalus, viewed using a UV epifluorescence microscope and marked with alizarin complexone. The chub is a very common species of freshwater fish in Europe. Otoliths are mineral concretions found in the inner ear of vertebrates. They 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). In this image, we can clearly distinguish…

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…

Barbel egg, Barbus barbus, 7 days after fertilization. Laboratory experiments on the barbel help improve understanding of the characteristics of its life cycle, notably the crucial stages of its development. In particular, research scientists can study its growth thanks to otoliths. They can then target actions to promote the ecological restoration of this species. Indeed, the barbel is a species characteristic of several areas of the Rhône whose life cycle is affected by the numerous…

Sanding of a lapillus, a type of otolith taken from a chub, Squalius cephalus, a very common species of freshwater fish in Europe, 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 …

Barbel larva, Barbus barbus, 4 days after hatching, in which the otoliths – mineral concretions found in the inner ear of vertebrates – can be distinguished (in brown). 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). Otoliths can also be used to work out an approximate hatching date, and thereby the length of the reproductive period of the species…

Frontal section of a lapillus, a type of otolith taken from a juvenile chub, Squalius cephalus, a very common species of freshwater fish in Europe, viewed using an optical microscope (700x with immersion). 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…

Frontal section of a lapillus, a type of otolith taken from a juvenile chub, Squalius cephalus, a very common species of freshwater fish in Europe, viewed using an optical microscope (700x with immersion). 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…