WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2024 55 the Center, with 30 PLs randomly selected to estimate average length and weight. The average length was 0.5 cm and average weight was 1 mg. Finally, PLs were stocked in research tanks under four different stocking densities and Almond (Terminalia catappa) leaves were added to each tank. The study utilized a Completely Randomized Block Design. There were four treatments (0.75, 1.25, 1.75 and 2.25 PL/L) with four replicates for each treatment. Initially, PLs were reared using a chicken egg mixture and Artemia (Figure 3) until they reached two weeks of age. Feeding frequency was five times per day, at 3-hour intervals. After this time, formulated powder feed (40 percent crude protein) was offered (Figure 4). Thereafter the daily feeding amount was increased every two weeks to 25 percent of body weight. During the study period, the behaviors of fish were closely observed for the identification of stress conditions. Water quality was monitored throughout the study to prevent the occurrence of disease and to maintain the health of experimental fish. If water quality is not acceptable, chances of parasitic diseases such as white spot or Trichodina are high in Dambulla. The Dissolved Oxygen (DO) level, temperature and pH of the water in tanks were measured daily using portable meters (Figures 7 and 8), calibrated at 3-day intervals. All tanks were siphoned daily, removing half of the water (Figure 9) and refilling with the same amount of new water. Almond leaves (as a natural remedy to cure any infection the fish might have) were added at 2-day intervals. Body weight and length were measured at 2-week intervals (Figures 10 and 11). In each tank, the length and weight of 30 randomly selected fish were measured in the morning to reduce stressful conditions associated with warmer temperatures later in the day. Weights were measured using an electronic balance and lengths were measured using a ruler. The following parameters were calculated using the below equations: • Weight gain = Final weight (g) – Initial weight (g) FIGURE 12. A sample of fry for data collection. FIGURE 11. Length measurement. (CONTINUED ON PAGE 56) TABLE 1. Final Mean weight and mean length of 61-day old S. spilurus under different stocking densities. Treatment Initial Stocking density Final mean length (cm) Final mean weight (g) T1 0.75 PL/L 3.3±0.01a 0.464±0.013a T2 1.25 PL/L 2.8±0.05b 0.314±0.008b T3 1.75 PL/L 2.4±0.06c 0.218±0.014c T4 2.25 PL/L 2.0±0.05d 0.124±0.005d Results are expressed as mean ± standard deviation of the mean. All treatments were significantly different.
RkJQdWJsaXNoZXIy MjExNDY=