Etude préliminaire à l'évaluation de l'activité reproductrice du rorqual commun en Méditerranée

Hormonal evaluation of reproductive status on fin whales in the Pelagos Sanctuary. The purpose of this study was to estimate the possibility of following the reproductive activity of rorquals by means of cutaneous biopsies on which steroids stored in subcutaneous fat were measured. During 2 seasons (from June till September, 2010 and 2011), about 150 biopsies were collected in the north-western Mediterranean. The sex was determined through the amplification of the specific DNA fragments of the gene ZF-X and ZF-Y. Steroids were extracted from fat by heating and measured by radioim- munology. The results show that at least a third of females are pregnant and that two thirds of males have a status of active stallion. It is still difficult to establish the state of the females which do not present a high progesterone rate because the hormonal varia- tions during the cycles are still badly known. This study shows that its protocol can allow to estimate the reproductive activity of fin whales. It could evolve with the aim of improving knowledge of the cyclic variations of females and detecting the possible births from a sea- son to an other.