Changes in serum cortisol, metabolites, osmotic pressure and electrolytes in response to different blood sampling procedures in cultured sea bass (Dicentrarchus labrax).

This study investigated the e€ect of ®ve sampling procedures on serum cortisol, glucose, total protein, osmolality, Na+, Cl±, K+ and Ca++ concentrations in 2-year-old cultured sea bass (Dicentrarchus labrax L). Mild disturbance caused by rapid removal of fish and brief handling did not induce signi®cant variation in any of the blood parameters investigated. Confinement and crowding elicited a high and signi®cant increase in serum cortisol, glucose, osmolality, Na+, Cl± , and Ca++ concentrations. Exposure to MS 222 (140 mg L±1) significantly increased osmolality, but not ionic concentration. Site of blood withdrawal (cardiac sinuses/caudal vein) had no effect on the concentration of analysed blood constituents, except for K+ levels. Scattered literature of sea bass blood chemistry is reviewed and compared with `normal' ranges of blood constituents measured in this study. We conclude that it is necessary to select and rigorously execute an opportune blood sampling procedure whenever blood constituents are used as indicators of fish functional state.