Transport of juvenile dusky grouper Epinephelus marginatus under different packing densities: Metabolic and haematological responses

The aim of this study was to investigate a suitable packing density for the transport of juvenile dusky grouper, Epinephelus marginatus, based on the evaluation of stress responses in blood. After acclimation, fish were placed in plastic bags and transported for 8hr on paved road at densities of 28, 45 and 64g/L. Water quality was monitored before and after transport. Blood was collected before, upon arrival (0hr), after 2 and 24hr of transport. Plasma cortisol, blood glucose, partial pressures of O-2 (pO(2)) and CO2 (pCO(2)), blood pH and HCO3- were evaluated. Blood smears were prepared for the verification of leucocyte profile and neutrophils:lymphocyte ratio (N:L). Blood pCO(2), pH and HCO3- increased significantly after transport for all treatments compared with pre-transport. Glucose levels increased at the higher density whereas no effects were observed on plasma cortisol and pO(2) levels. Upon arrival, all treatments showed lymphopenia and neutrophilia which increased N:L ratio. Although lymphopenia was observed in higher densities until 2hr after transport, haematological parameters were fully restored within 24hr post transport. Furthermore, no mortalities were observed throughout the experimental period. Based on the transient physiological changes observed in this study, juvenile dusky grouper can be safely transported in plastic bags for 8hr at a density of up to 64g/L.