The Effects of Salinity on Postlarval Growth and Survival of Penaeus semisulcatus (Decapoda: Penaeidae)


Abstract: P. semisulcatus post-larvae (PLs) had higher survival and better growth at high rather than low salinities between PL20 and PL60. Final survivals at high salinities (30-40 ppt) (19-23%) were significantly higher than those (3-12%) below 25 ppt (P<0.05). Final total length (TL) at 10 ppt (17.12 mm) and 15 ppt (17.12 mm) was significantly lower than at 35 ppt (20.46 mm) or 40 ppt (19.62 mm) (P < 0.05). PLs grown at 10 and 15 ppt displayed growth rates between 0.053 and 0.068 mm day^{-1} as compared to 0.115 - 0.137 mm day^{-1} at higher salinities (35-40 ppt). Daily growth rates at salinities above 30 ppt (0.114-0.137 mm day^{-1}) were about 2-2.5-fold higher than those obtained at 10 ppt (0.053 mm day^{-1}). PLs grown at 10 and 15 ppt attained the lowest individual wet weight (0.020 - 0.037 g) while those at 35 and 40 ppt had the highest mean weight (0.050-0.051 g) at the end of the 40-day culture period (P < 0.05). The results showed that the mean weight obtained at 40 ppt was twice that at 10 ppt. PLs grown at 15, 20 and 25 ppt exhibited intermediate growth in weight (P > 0.05). A rise in salinity resulted in an increase in the biomass from 0.020 g at 10 ppt to 0.317 g at 40 ppt (P < 0.05). Optimum salinity for the nursery culture of P. semisulcatus PLs appeared to be about 40 ppt at 28 °C. Hence, the results of this study demonstrate that P. semisulcatus inhabiting the Mediterranean Sea is not a good candidate for culture in waters of low salinity.

Keywords: Penaeus semisulcatus, salinity, post-larvae, growth, survival

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