Morphologie, croissance individuelle et dynamique des populations de la tortue verte (Chelonia mydas L.) au banc d'arguin (République islamique de Mauritanie)

Abstract

The carapace morphology and growth of the Green turtle (Chelonia mydas L.) has been studied in a large (n = 177) sample of animals collected by the Imragen fishermen on the Banc d'Arguin (lslamic Republic of Mauretania). The frequency of anomalies of the scales decreases with age in this species, possibly due to a differentiai mortality between normal and abnormal individuals. The mathematical relation between length and width of the carapace is discussed and the Mauretanian data are compared with those of other areas. There are obvious differences in the shape of the carapace between different breeding populations of green turtles, which quite likely correspond to genetic differences between various breeding populations. The Mauretanian green turtles are quite similar to those breeding on the eastern coast of South-America. Seven age classes can be recognized on the basis of the carapace length. A growth curve of the Mauretanian population of Chelonia mydas L., based upon von Bertalanffy equation, is proposed. The rate of growth decreases sharply after the first breeding season. Sexual maturity takes place at 5.5 years of age, but age at first reproduction apparently varies from one population to the other, probably depending upon fishing pressure. The number of "bachelors" (mature individuals not taking part in reproduction) is apparently greater in areas with the smallest fishing pressur