Female reproductive biology of the bluemouth Helicolenus dactylopterus dactylopterus: spawning and fecundity.

The bluemouth Helicolenus dactylopterus dactylopterus is a zygoparous species that spawns multiple batches of embryos enclosed within a gelatinous matrix. Oocyte development is asynchronous, and the recruitment of secondary growth oocytes occurs continuously during the developing phase, but stops before the start of the first spawning (i.e. fecundity is determinate). The number of developing oocytes can be estimated as a function of the total length of the fish, its ovary mass and its gonado-somatic index. Only at the onset of spawning, when potential fecundity is determined, does condition also have a significant effect. The low levels of atresia detected during most of the spawning season show that this mechanism does not substantially affect the process. There is variability both in the spawning interval (with a mean of 2 days) and in the number of embryos comprising every single batch (up to 37,000). Expected effect of fisheries on the reproductive traits of this deep-sea species is also discussed.