POTASSIUM FLUX IN JUVENILE STRIPED BASS (MORONE-SAXATILIS) - INFLUENCE OF EXTERNAL CONCENTRATIONS OF SODIUM-CHLORIDE AND CALCIUM

Whole-body influx and efflux of K+ were determined for 25-day-old stri ped bass, Morone saxatilis, in conditions that simulated harvesting fi sh from ponds. During the first 5h in fresh water with combined high N aCl (80 mM) and low Ca2+ (0.12 mM) concentrations, a combination that is acutely lethal to this age of striped bass, K+ influx for fish in 0 .07 mM K+ was 21 +/- 1.7 (SEM) compared to 3.4 +/- 0.33 nmol g(-1) h(- 1) for fish in water with low Na+ (0.25 mM) or high Ca2+ (2.5 mM) conc entrations. Influx of K+ was inhibited during the first few hours afte r fish were placed in flux chambers. Potassium efflux as percentage of K-42 lost per hour was two-fold higher from fish in the high Na-low C a treatment compared to fish in low concentrations of Na+ or high conc entrations of Ca2+. Potassium efflux was probably much greater than in flux, but exact values for efflux could not be calculated from the dat a available. Survival of fish in water with high Na-low Ca was not inc reased by addition of KCI to the water, indicating chat the net loss o f Ki was probably not the cause of death.