Increased postharvest survival of young white bass and sunshine bass by addition of calcium and sodium chloride to soft water

Postharvest survival of white bass Morone chrysops and sunshine bass M. chr ysops female x Morone saxatilis male was determined in water containing add itional NaCl, CaCl2, MgCl2, or combinations of these salts. Age of fish was near the time of metamorphosis from larval to juvenile stages; white bass were 23 d old and sunshine bass were 30 d old. All white bass confined in 2 -L beakers died within 7 h in soft water (2.5 mg Ca2+/L), and addition of N aCl (0.7-5.0 g/L) alone did not increase survival. Addition of 35 mg Mg2+/L to water containing 5.0 g NaCl/L increased survival to 57% after 7 h, but only 7% survived for 24 h. In tests with various concentrations of Ca2+ (2. 9-20 mg/L) and 5.0 g NaCl/L, survival rate increased with increasing concen tration of Ca2+ up to 85.7% at 14 mg/L, and a higher concentration of Ca2did not increase survival. A Ca2+ concentration of 9.1 mg/L (95% confidence interval, 7.5-10.9) was needed to achieve 50% survival for 7 h. Few white bass died after 7 h in the Ca2+ experiments. Amiloride, a sodium transport inhibitor, added to the water did not affect survival. All sunshine bass we re dead after 19 h in containers with 10 L of soft water (2.0 mg Ca2+/L), a nd only 25% survived in water with 5.0 g NaCl/L. Addition of 84 mg Ca2+/L i ncreased survival to 64%, and addition of both 93 mg Ca2+/L and 5.0 g NaCl/ L resulted in 91% survival. Results for white bass and sunshine bass were g enerally similar to those of previous studies with striped bass M. saxatili s at this stage of development.