Effects of different loading densities during transport on survival rates of Asian seabass (Lates calcarifer Bloch, 1790) juvenile

This study was carried out to evaluate effects of loading density on water quality and survival rate of Asian seabass (Lates calcarifer) juvenile during live transport. The experiment included four treatments of different biomass: 50 kg/m3 (T1), 70 kg/m3 (NT2), 90 kg/m3 (T3) and 110 kg/m3 (T4) with three replicates for each treatment. The fish with an average weight of 20.50±0.25 g and length of 11.52±0.22 cm were fasted for 24 h before transporting in aerated and oxygenated heat-insulating tanks. The water temperature in transport was set at 22⁰C and the concentration of isoeugenol was 6 ppm. The fish was acclimatized to the transport temperature by gradually cooling water with ice to 22⁰C for 30 minutes. Then, fish were transferred to transport tanks containing 40 L water and closed with lids. After transporting, the fish were kept in hapas suspended in an earthen pond with routine management. Water quality and survival rates of the fish were recorded after transport 6 h and 12 h (end of experiment), and 3 and 7 days after the end of transporting. The results showed that the water quality was declined expressed by the decrease of DO and pH, and the increase of CO2, TAN and NO2 during transport but still in suitable ranges for seabass. The survival rates of the fish of all treatments were reduced following transport duration. The fish were well recoverd after the transport. At the end of the study, the survival rate of the fish of T1 was highest (96.00%), followed by T2 (95.33%), T3 (90.00%) and T4 (87.63%). Based on accumulated mortality, loading biomass of 70 to 90 kg/m3 and 50 to 70 kg/m3 were reccomended for live transport of seabass juvenile in cooling water (22⁰C) and sedation with isoeugenol (6 ppm) during 6 h and 12 h, respectively.