Abstract
The rose bitterling Rhodeus ocellatus ocellatus, Cyprinidae, a spring and summer breeder, were captured in out of the breeding season (early November). They were divided into three temperature groups (5, 10, and 15°C), and reared under a short photoperiod (1OL-14D) for 60 days. Then each group was divided into two photoperiod groups; a long (14L-10D) and the short (continued) photo-period group, and all the groups were kept at 15°C for another 37 days. In females gonadal re-crudescence did not occur in any temperature group during first 60 days. However at the end of the experiment (late February), gonadosomatic indices (GSIs) of ovaries had significantly increased in all the long photoperiod groups. On the other hand, only the females pre-treated by warmer temperatures (10 and 15°C) for 60 days showed some gonadal recrudescence under the short photo-period. Male bitterling represented almost the same pattern of the change of GSIs during the experiment, but some individuals had attained the spermiogenesis in all the groups at the end of the experiment. These results indicate that in the post spawning season, the photoperiodism in-volved in maturation of the rose bitterling declines under natural temperatures of late autumn (10-15°C). Low temperatures of winter do not seem to be essential for the gonadal maturation in spring during the annual reproductive cycles of this species.
