Date Received: 03-01-2018 / Date Accepted: 17-08-2018
This study was conducted to examine the effect of salinity fluctuation frequency on molting rate and growth of postlarval white-leg shrimp (Litopenaeus vannamei). Individal shrimp was stocked in 5 L plastic bottle containing 2 L of 20 ‰ seawater with 04 treatments including salinity fluctuation in an amplitude ± 0‰ (NT1; ĐC), and an amplitude ± 5‰ with a frequency was set in 2 days (NT2), 4 days (NT3) and 6 days (TN4), 30 replicates each. The initial weight and length of postlarva was 0.007 g/ind. and 0.97 cm/ind., respectively. The results showed that the shorter molting frequency (4.9 days/times) and higher molting rate (22.1 %/day) were obtained in the treatment (NT4) where salinity fluctuation frequency was set in 6 days. In contrast, longer molting frequency (5.3 days/times) and lower molting rate (20.5 %/day) was obtained in the constant salinity treatment (ĐC). In addition, the highest growth in terms of weight after 45 days culture were obtained in NT4 (0.88 g/ind.), followed by NT3 (0.85 g/ind.), NT1 (0.83 g/ind.), and NT2 (0.74 g/ind.). The results of this study indicated that the higher molting rate and shorter molting frequency lead to significantly better growth of shrimps when salinity fluctuation in 6 days frequency was applied, compared to constant salinity.
