Effect of temperature and photoperiod on the reproductive condition and performance of a tropical damselfish <Emphasis Type="Italic">Chrysiptera cyanea</Emphasis> during different phases of the reproductive season |
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| Authors: | Mohammad Abu Jafor Bapary Akihiro Takemura |
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| Institution: | (1) Department of Biology, Chemistry and Marine Sciences, University of the Ryukyus, 1 Senbaru, Nishihara Okinawa, 903-0213, Japan; |
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| Abstract: | Effects of temperature and photoperiod on the reproductive activity of a reef associated tropical damselfish Chrysiptera cyanea were evaluated under three phases with different environmental patterns, phase I (April–May; increasing water temperature
and photoperiod), phase II (June–July; increasing water temperature and peak/decreasing photoperiod), and phase III (August–September;
peak/decreasing water temperature and decreasing photoperiod). When the fish were reared at 20, 25, or 30°C under natural
photoperiod, the reproductive conditions differed within and among the phases depending on experimental temperature and environmental
patterns. From phases I through III, ovaries with vitellogenic oocytes were notable only at 25°C, whereas regressing and immature
oocytes were noticed at 20 and 30°C. The fish underwent active spawning at 25°C, whereas no or few spawnings were observed
at other temperatures. In phase III, there was a resultant prevention of decrease in the gonadosomatic index and disappearance
of vitellogenic oocytes in the ovaries of fish under a long photoperiod (LD14:10) compared to those under a short photoperiod
(LD10:14). These results indicate that a long photoperiod with a suitable range of water temperature is a principal determinant
in continuity of reproductive activity and performance, and that a high temperature has a negative impact on their ovarian
development. |
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