Change in rigor mortis of red sea-bream dependent on season and killing method

The ATP/IMP ratio of stressed fish muscle in summer (from June to August) w as lower at the initial stage than the ratio in winter (from January to Mar ch), and reached to the ultimate value 3 h earlier. Though stressed fish mu scle in summer showed larger contraction than that in winter, almost the sa me tension values were observed in both seasons. This result was ascribed t o the structure weakening due to large contraction in summer. The ATP/IMP ratio of unstressed fish muscle in summer was lower at the init ial stage than the ratio in winter, and reached to the ultimate value 4 h e arlier. The initial ATP/IMP ratios of spinal cord destroyed fish muscles at two seasons were both high values. The ratio in summer was slightly lower at the initial stage than the ratio in winter, and reached to the ultimate value 10 h earlier. Unstressed and spinal cord destroyed fish muscles in su mmer contracted more than those in winter, and showed larger tension values . This result means that the structure weakening was not remarkably induced in the muscles obtained in summer. In spinal cord destroyed fish muscles t he slow but continuous tension development induced the structure weakening. Therefore the tension increment in summer was not as large as in unstresse d fish muscle.