OOGENESIS DYNAMIC AND SPAWNING OF THE DAB , LIMANDA-LIMANDA, FROM THEWESTERN COAST OF BRITTANY AND THE ENGLISH-CHANNEL

In order to describe oogenesis and the mechanism of spawning in the da b, Limanda limanda (L., 1758) the ovaries of 74 females caught on the western coast of Brittany (the Bay of Douarnenez) and in the English C hannel (the Bay of Seine) were investigated. A microscopic scale inclu ding six oocyte developmental stages was used to classify oocytes. Cor tical alveoli which appeared in the peripherical cytoplasm were the fi rst microscopic features of vitellogenesis; they were present in 120 m u m diameter oocytes, the threshold size to be retained for fecundity studies. In ovaries of precocious females there was a gap between prev itellogenic and vitellogenic oocytes before beginning of spawning, thu s the dab must be considered as a species with a determinate fecundity . The intensity of atresia was low and the annual fecundity was nearly the same as the potential annual fecundity. On the other hand in ovar ies of females with later spawning, vitellogenic oocytes which were un spawned at the end of spring degenerate.