Hematological and Osmotic Changes of Seabass, Lates calcarifer under Salinity Shock

The seabass, Lates calcarifer is one of the commercially important cultured species in Taiwan. The objective of this research is aimed to document the physiological responses of this species under acute salinity shock. Fish were acclimated at a salinity of 25ppt for 2 weeks and then transferred directly to salinity extremes of either 5 or 45ppt. Changes in physiological, hematological and osmotic parameters of the seabass were monitored for a 24-h period. The tolerability of the seabass to the salinities of 5ppt to 45ppt is clearly demonstrated by their survival and capabilities of physiological compensation. The possibility of the seabass being cultured in water bodies with a wide range of salinities is further confirmed. Marked increases in the plasma osmolality, corresponding to environmental salinities, were noted over the 24-h period, although the plasma osmolality of the seabass remained at a relatively stable level of 274.6~350mOsm kg^(-1). The parallel changes of osmotic components of Na(superscript +) and Mg(superscript +) with the blood osmolality were further noted, while the blood K(superscript +) concentrations were inversely decreased. The status of energy metabolism, indicated by the oxygen consumption and hyperglycemic responses are notably enhanced in both salinity extremes conditions. Similar changes in the respiratory constituents involved in oxygen-carrying capacity are further demonstrated. The present study indicated that the compensation process of the fish to altered environmental salinities is evidently reflected in the physiological processes of osmotic regulation, energy metabolism, and respiratory capacity indicated respectively by the blood osmolality and ion osmolarity, oxygen consumption and hyperglycemic responses, and respiratory pigments.