Carp were acclimated to 10 and 30°C, and examined for rigor mortis progress, along with ATP and creatine phosphate degradation and lactate accumulation, during storage at 0, 10, and 20°C. Rigor mortis progress and related biochemical changes were slower with the cold-acclimated than with the warm-acclimated carp during storage at 0 or 10°C, and vice versa at 20°C. Myofibrillar Mg2+- ATPase activity was higher with cold-acclimated than with warm-acclimated carp irrespec-tive of reaction temperature. Ca2+ uptake rate of sarcoplasmic reticulum (SR) from cold-ac-climated carp was higher than that from warm-acclimated one at reaction temperatures of 0 and 10°C, whereas, both groups did not exhibit any significant difference from each other at 20°C. Therefore, differences in rigor mortis progress during storage at 0 or 10°C between the cold- and warm-acclimated carp could have resulted from a slower Ca2+ uptake by SR of the warm-acclimat-ed carp at these storage temperatures, whereas differences at 20°C could be attributed to a higher myofibrillar Mg2+-ATPase activity with the cold-acclimated carp.
