Effect of transport density on survival rate of black seabream sealed in oxygenated plastic bag during stock enhancement

To investigate the optimum transport density and post-transport recovery for juvenile black sea bream (Sparus nacrocephalus) during the stock enhancement, we sealed the juveniles (length of 9–11.7 cm) by oxygenated plastic bags and transported them for 2.75 h at different densities (10 ind., 15 ind., 20 ind., 25 ind. and 30 ind.) at sea water temperature of 27.7 ℃, sainilty of 29, pH of 8.04 and dissolved oxygen of 8.8 mg·L^–1. Then we observed the effect of transport density on the total protein (TP), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) in serum and muscle at 0^th, 6^th, 12^th, 24^th and 48^th hour. The results show that the TP and MDA concentrations in serum and muscle in groups of 10 ind. and 15 ind. were lower than that in group of 30 ind. after transport (P<0.05); while the situation was just on the contrary for the activities of SOD and CAT (P<0.05). In the aspect of recovery level, groups of 10 ind. and 15 ind. had the best recovery of the indicators in serum and muscle, followed by groups of 20 ind. and 25 ind. while group of 30 ind. had the slowest recovery and failed to fully recovery at the end of the experiment. In consideration of economic factors, 25 ind. per bag is recommended when the 9–11.7 cm juvenile black seabreams are transported for 2.75 h at water temperature of 27.7 ℃, salinity of 29 and pH of 8.04 sealed in oxygenated plastic bag.