Transport of Scylla serrata megalopae at various densities and durations

Abstract

The optimal conditions for transport of Scylla serrata megalopae were determined. Loading densities of 50, 100 and 150 ind l⁻¹ of hatchery-reared megalopae were studied over a 6-h simulated transport, including shaking. Survival immediately after transport was significantly higher at 50 ind l⁻¹ (99.3±1.6%) (mean±x%) than at 100 (93.0±5.0) and 150 ind l⁻¹ (94.0±3.8%). The same trend was noted 15 h after transport. Another experiment compared survival of megalopae packed at 50 and 100 ind l⁻¹ with simulated transport of various durations (3, 6, and 9 h) at mobile and stationary conditions. Regardless of the duration and condition of transport, survival was again significantly higher at 50 ind l⁻¹ (86.7±2.4%) compared to 100 ind l⁻¹ (79.7±2.1%). Megalopae that were shaken or remained unshaken for 3 or 6 h had similar survival through transport as those shaken for 9 h. Megalopae that remained unshaken for 9 h gave the lowest survival among treatment groups (38.7±0.2%).

Due to cannibalistic behavior, stationary transport conditions may have provided the megalopae with a chance to grasp each other. In a third experiment, a batch of megalopae was packed at water temperature levels of 20, 24, and 28°C (ambient) at 50 and 100 ind l⁻¹ for 6 h simulated transport, including shaking. Density and temperature separately influenced survival. Survival was lower at 28°C than 24°C. Although megalopae were less active at 20°C, survival was similar to that at 24°C and 28°C. These results provide useful information for megalopae transport from hatchery to ponds.