| Abstrakt: |
In temperate regions freshwater prawn, Macrobrachium rosenbergii , juveniles are nursed to more advanced sizes ( $0.3 g) in indoor tanks, then transported to ponds for growout. Stress during transport can produce immediate mortality and undetected mortality after pond stocking. This study was designed to evaluate the effect of biomass density during transport in sealed containers on pre-stocking prawn survival. Nine replicate styrofoam transport containers were prepared. Each contained one double bagged plastic bag with 10 L of oxygen-saturated 22EC water with an atmosphere of 10 L pure oxygen. Juvenile prawn weighing 0.26±0.02 g (average weight ±S.D.) were randomly stocked into transport containers at either 10, 25 or 50 g of prawn per liter of water, then sealed for eight hours (maximum regional transport period). There were three replicate transport containers per density. At eight hours post-stocking, bags were opened, water quality determinations were conducted, and live and dead animals were separated and counted. Total ammonia-nitrogen and un-ionized ammonia-nitrogen concentrations were significantly higher ( P # 0.05) in containers stocked at 50 g/L than in containers stocked at either 10 or 25 g/L, which were also significantly different ( P # 0.05) from each other. Nitrite-nitrogen concentrations were significantly higher ( P # 0.05) for containers stocked at 50 g/L than in those stocked at 10 g/L. However, nitrite concentrations in containers stocked at 25 g/L were not significantly different ( P > 0.05) from containers stocked at other densities. Dissolved oxygen was significantly lower ( P # 0.05) in transport containers stocked at 50 g/L (1.3 mg/L) than those stocked at 25 g/L or 10 g/L (1.6 mg/L and 3.2 mg/L, respectively), which were also significantly different ( P # 0.05). Survival was significantly lower ( P # 0.05) in transport containers stocked at 50 g/L (86.6%) than in containers stocked at 25 g/L (93.0%) and 10 g/L (97.2%), which were also significantly different ( P # 0.05). These data indicate that transport densities greater than 10 g/L should be avoided for transport $ 8 hours in sealed containers. [ABSTRACT FROM PUBLISHER] |
