a1 Laboratoire de Biologie Animale, Faculté des Sciences, Avenue Victor Le Gorgeu, 29287 Brest Cedex, France
The population structure of the thornback ray, Raja clavata L., expressed in terms of length and sex, seems to be related to hydrological conditions prevailing on the sampling areas. In the exposed area (Cove of Bertheaume), females are more frequently captured than males, and indeed represent the entire catch in the summer. In contrast, in the relatively sheltered area (Bay of Douarnenez) a majority of adult males and immature females are caught.
After winter, only adults and juveniles of Raja clavata migrate into the Bay of Douarnenez. This bay may be a mating area for adults and also a nursery for juveniles particularly for immature females.