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 8 hr on paved road at densities of 28, 45 and 64 g/L. Water quality was monitored before and after transport. Blood was collected before, upon arrival (0 hr), after 2 and 24 hr of transport. Plasma cortisol, blood glucose, partial pressures of O₂ (pO₂) and CO₂ (pCO₂), blood pH and HCO₃^? were evaluated. Blood smears were prepared for the verification of leucocyte profile and neutrophils:lymphocyte ratio (N:L). Blood pCO₂, 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 pO₂ levels. Upon arrival, all treatments showed lymphopenia and neutrophilia which increased N:L ratio. Although lymphopenia was observed in higher densities until 2 hr after transport, haematological parameters were fully restored within 24 hr 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 8 hr at a density of up to 64 g/L.