Drinking rates of stressed one-month-old striped bass: Effects of calcium and low concentrations of sodium chloride

Drinking rates for striped bass Morone saxatilis were measured in freshwate r and in water with a physiologically hypotonic concentration of NaCl (5 g/ L). Fish were 27 d old (posthatching) and had recently completed larval de velopment. Drinking rates were determined without allowing fish to adjust t o test conditions because problems with survival of young striped bass ofte n occur when they are stressed. In water with 5 g NaCl/L and 3.7 mg Ca2+/L, a combination of ions lethal to stressed striped bass at this stage of dev elopment, mean drinking rate (+/-SE) was 4.7 +/- 0.3 mu L . g(-1) . h(-1). This drinking rate was significantly higher than the mean drinking rate (1. 8 +/- 0.2 mu L . g(-1) . h(-1)) in water with 5 g NaCl/L and 100 mg Ca2+/L. Drinking rare in ion-poor water (5.8 mg Na+/L and 3.7 mg Ca2+/L) was only 0.38 +/- 0.05 mu L . g(-1) . h(-1). Drinking rates measured for 1 h or 3 h did not differ significantly, indicating that changes in drinking rates occ urred quickly. High drinking rates may contribute to the death of young str iped bass when there is an imbalance between environmental concentrations o f NaCl and Ca2+.