Oocyte development in summer flounder: seasonal changes and steroid correlates

Seven ovarian stages are described in summer flounder Paralichthys dentatus . in the prespawning season plasma oestradiol levels increased in maturing fish with lipidogenic oocytes and gonadosomatic index increased in fish und ergoing vitellogenesis. Atretic oocytes present in the postspawning season indicated which individuals may have spawned. The pattern of oocyte develop ment is similar to that of other flatfishes and some teleosts. The summer f lounder was unusual in having a long lipid uptake phase (oocyte diameter up to 301 mu m) prior to any indication of vitellogenin (yolk protein) uptake . This information will be useful in the construction of an updated maturit y schedule for the wild population. (C) 2000 The Fisheries Society of the B ritish Isles.