Influence of Salinity, Temperature, and Exercise on Plasma Osmolality and Ionic Concentration in Atlantic Salmon (Salmo salar)

Abstract

In unexercised Atlantic salmon (Salmo salar), plasma osmolality and Na+ and Ca++ concentrations varied little at temperature-salinity combinations of 3, 5, 10, and 14 C and 0, 15, and 30‰. Plasma K+ tended to increase with increase in temperature. Cl− values were similar at 5 and 14 C. At 1 C and 0‰, lower plasma osmolalities indicated reduced ability to osmoregulate. At 1 C and 30‰, elevated osmolalities and ionic values and mortalities indicated severe osmotic stress.After exercise for 2 hr at 3–4 body lengths/sec at 5 and 14 C, salmon in salinities of 0 and 15‰ had osmolalities and ionic values the same as or little changed from unexercised values. There were marked increases in the values following exercise in 30‰.