Effects of temperature and salinity on larval growth, survival and development of Penaeus semisulcatus

Four temperatures (22 degrees C, 26 degrees C, 30 degrees C and 34 degrees C), and the combined effects of three salinity (25, 30 and 35 ppt) and three temperature (26 degrees C, 30 degrees C and 34 degrees C) levels from protozoea 1 (PZ1) to postlarvae 1 (PL1) stages of Penaeus semisulcatus were studied in two separate experiments. In the first experiment, the PZ1 larvae at the lowest temperature of 22 degrees C showed the highest survival (69%) to PL1 compared to 61% at 26 degrees C, 44% at 30 degrees C and 12% at 34 degrees C. However, 22 degrees C slowed the growth and delayed the larval development by about 2-4 days. Growth rate at 30 degrees C (0.44-0.48 mm day(-1)) was double of that (0.22-0.25 mm day(-1)) at 22 degrees C. The results showed that P. semisulcatus is tolerant to low, rather than to high temperatures during the larval development. Hence, a water temperature; level of about 30 degrees C is optimal for the larval culture of this species. The second experiment showed that temperature exerted a greater influence than the salinity on the growth and survival during the larval development. The range of temperature in which the larvae showed high survival and growth is relatively narrow as compared to that of salinity. At all salinity levels, survival to PL1 (69-77%) was higher at 26 degrees C as compared to 30 degrees C (44-73%) and 34 degrees C (14-21 degrees), However, daily growth rate at 30 degrees C and 34 degrees C was about 60% higher than at 26 degrees C. Larval development was also 3-4 days faster at 30 degrees C and 34 degrees C. Based on the survival and growth results, the best salinity and temperature combination for the culture of P. semisulcatus was 30 Dpt and 30 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.