Effects of transport density and duration on transport water quality, resuscitation rate and antioxidant ability in juvenile Lates calcarifer

The experiment was conducted to investigate the effects of simulated transportation for 24 h with three transport densities (D1=14 kg·m⁻³, D2=21 kg·m⁻³, D3=28 kg·m⁻³) and six different transport durations (T1=4 h, T2=8 h, T3=12 h, T4=16 h, T5=20 h, T6=24 h) at 7 kg·m⁻³ on the transport water quality, resuscitation rate and antioxidant capacity of juvenile Lates calcarifer. The results show that with the increase of transport density and duration, the contents of NH₄ ⁺-N and NO₂ ⁻-N in the transport water increased, while the DO content, pH and resuscitation rate decreased but the survival rate was 100%. The results of transport density test show that the T-SOD activities in D1 and D2 groups were significantly lower than that in the control group (P<0.05); the POD activity in D3 group were significantly lower than those in D1 group, D2 group and the control group (P<0.05); the MDA content in D2 group was not significantly different from that in D3 group, which was significantly higher than those in D1 group and control group (P>0.05). The results of transport time test show that there was no significant difference in T-SOD activity between T3 and T4 groups, which were significantly higher than those in T1, T2, T5 and T6 groups (P<0.05); the POD activity in each experimental group was significantly higher than that in the control group (P<0.05); the MDA content in T2 group was not significantly different from that in T4 group, but was significantly higher than those in T1, T3, T5, T6 groups and control group (P<0.05). It is shown that with the increase of transport density and duration, the water has deteriorated and the resuscitation rate decreased, having significant effect on the antioxidant ability of L. calcarifer juveniles. In conclusion, under conditions of water temperature 24 ℃, salinity 32 and pH 7.92, with body length of (1.42 ± 0.19) cm, the density should not exceed 21 kg·m⁻³ for 24 h.