The changes of resting metabolism (RM) with rapid lowering of water temperature and myofibrillar (Mf) Mg2+-ATPase activity at different temperatures were determined by using 14 species of fish collected from four waters: Sakishima Islands (28°C), Amami-Oshima (25°C), the sea adjacent to Nagasaki (22°C), and the Yellow Sea (10°C).
Both mean values of RM and Mf Mg2+-ATPase activity of fish at a certain habitat temperature tended to decrease with the lowering of habitat temperature, while the opposite results were observed under the same temperature. There exists a positive thermal compensation in fish in habitats of low temperature. The temperature dependences of RM and Mf Mg2+-ATPase activity were found to be the largest in fish in the Yellow Sea, but tended to be smaller with the decrease of habitat temperature in the other three waters. These results were caused by the fact that the Arrhenius plots of Mf Mg2+-ATPase activity showed a break in slope at near 15°C in all fishes.
A significant positive correlation was found between both the values of RM and Mf Mg2+-ATPase activity at habitat temperature and their temperature dependences. The results suggested that the RM and Mf Mg2+-ATPase activity were closely related.
