INFLUENCES OF TEMPERATURE UPON THE POSTEXERCISE PHYSIOLOGY OF ATLANTIC SALMON (SALMO-SALAR)

Atlantic salmon (Salmo salar) were acclimated and exhaustively exercis ed at 12, 18, or 23 degrees C to determine how temperature influences the magnitude of postexercise physiological disturbances. At each temp erature, exercise led to decreased white muscle ATP and phosphocreatin e concentrations. Phosphocreatine was rapidly restored within 1 h at e ach temperature whereas ATP restoration took 1-4 h at 18 and 23 degree s C, but considerably longer at 12 degrees C. Exercise-induced depleti ons of white muscle glycogen were accompanied by elevations in muscle lactate, which contributed to 0.6 unit decreases in white muscle intra cellular pH (pH(i)) at each temperature. Compared with rates of recove ry in warmer water, glycogen resynthesis, lactate catabolism, and pH(i ) correction were slower at 12 degrees C. White muscle REDOX state est imates suggested that slower postexercise recovery at 12 degrees C was not due to oxygen delivery limitations. Marked postexercise elevation s in plasma osmolality and lactate concentration were also observed an d in each case correction of the disturbance took longer at 12 degrees C. Paradoxically, significant mortality (30%) was observed only at 23 degrees C. We conclude that while warmer water facilitates postexerci se recovery of white muscle metabolic and acid-base status in Atlantic salmon, extremely high temperatures may make them more vulnerable to delayed postexercise mortality.