Simulated transport of Scylla serrata zoeae at various loading densities

Abstract

Percent mortality of mud crab Scylla serrata zoeae was determined after 6 h of simulated transport at mobile and stationary conditions at loading densities of 10, 20, 30 and 40 x 10³ ind-l^-1. Mortality was not significantly different among treatments immediately after transport. Surviving zoeae were stocked in basins, fed with Brachionus rotundiformis and mortality was compared 15 h after transport. There was no significant interaction between loading density and condition (mobile and stationary) of transport (P > 0.05). However, larval mortality varied significantly among densities (P < 0.001) regardless of the condition. A density of 10 x 10³ ind-l^-1 had the lowest mortality (0.56 ± 0.76%) followed by 20 x 10³ (1.28 ± 0.39%), 30 x 10³ (4.3 ± 0.25%), and 40 x 10³ (4.3 ± 0.31%) ind-l^-1. In another experiment, the effect of transport duration was determined at a constant loading density of 10 x 10³ ind-l^-1 in control (not subjected to packing and transport), shaken and unshaken conditions. Zoea mortality did not differ significantly (P > 0.05) after the 6, 9, and 12 h transport. Regardless of the duration, mortality was lowest in the control (0.41 ± 0.05%) compared to those in the shaken (0.99 ± 0.13%) and unshaken (0.79 ± 0.12%) conditions. Likewise, the condition but not the duration of transport affected larval survival at 15 h post-transport. Mortality was lower in the shaken (1.92 ± 0.22%) than in the unshaken condition (2.46 ± 0.17%). Since mortality is low even at 20 x 10³ ind-l^-1, this can still be used to transport S. serrata zoeae for 6 h. However, loading density should be reduced to 10 x 10³ ind-l^-1 for transport duration up to 12 h.