AN EFFECT OF WATER HARDNESS IN THE THERMAL RESISTANCE OF THE RAINBOW TROUT, SALMO GAIRDNERII RICHARDSON

Abstract

Two groups of Salmo gairdnerii were reared from fertilization in hard and soft waters, and the thermal resistance of the yearling trout was measured for both groups in soft and saline waters at 27, 28, and 29 °C. In all cases a history of rearing in soft water resulted in a greater resistance to thermal stress than did a history of rearing in hard water. Increased salinity of the testing medium resulted in an increase in thermal resistance.