MODIFICATION OF PHOTOPERIOD REDUCES EARLY SEXUAL MATURATION IN JUVENILE SEA BASS (Dicentrarchus labrax) (Hormonal aspects).

The effect of short-term exposure to continuous light (LL) to reduce early male sexual maturation was investigated in the sea bass. Four LL light regimes (1 or 2-month duration) were established during the pregametogenesis, whereas a simulated natural photoperiod (SNP) and a long-term exposure group (12-month duration) to LL were kept as controls according to previous trial in this species. Exposure to different LL treatments induced a differential response on the sex-steroid levels. Particularly, significant differences (ANOVA, n=20, P<0.05) in the levels of 11-KT were observed during the peak of reproductive period (February) in groups 4 and 5 (control) in comparison with groups 1, 2, 3, 6. These results suggested the role of this androgen as a putative threshold determining early puberty in the sea bass as previously reported. Profiles of T were similar during whole experimental period. E2 levels at the beginning of pregametogenesis (September) presented significant differences between SNP groups (5 and 2) and LL treatments groups (1, 3, 4, 6). Thus, the identification of a short-term exposure to LL approach can be of interest for sea bass aquaculture, since it could reduce the presence of early sexual maturing males under farming conditions.