Effects of photoperiod and temperature on molting, reproduction and growth of the freshwater prawn Macrobrachium rosenbergii.

Abstract

To investigate the combined effects of temperature and photoperiod on molting (reproductive molt, R; common molt, C), reproduction and growth of Macrobrachium rosenbergii, six groups of 14 females each were exposed to 12L12D or 15L9D, at 24, 28 or 32°C for a period of 140 days. Survival rates were satisfactory with the exception of treatment under 24°C/15L9D which caused high mortality. R frequency tended to increase with the elevation of the water temperature. Ex-posure to 32°C/12L12D significantly enhanced R frequency. Duration of molt intervals decreased with increased temperature. Both C-R and R-R intervals were longer than C-C intervals. Growth was faster at 28 and 32°C than at 24°C, and was enhanced under 12L12D. The highest condition factor was obtained under 28°C/12L12D. Increased temperature under 15L91D decreased growth rate after the occurrence of C-C. Under 12L12D growth rate decreased after the occurrence of C-R or R-R. Under any treatment, growth rate after R was lower than after C. Antagonistic interactions between reproduction and molting, and between reproduction and growth are evidenced and discussed.