Rigor Tension Development in Excised “Rested”, “Partially Exercised” and “Exhausted” Chinook Salmon White Muscle

Isometric rigorometry was used to study rigor tensions in “rested”, “partially exercised” and “exhausted” chinook salmon ( Oncorhynchus tshawytscha ) white muscle at the pre‐mortem acclimated temperature. Conservative handling and anaesthesia (AQUI‐STM) minimized pre‐mortem exercise and provided “rested” fish. Post‐mortem electrical stimulation produced “partially exercised” (180 contractions) and “exhausted” (360 contractions) muscle. A “relaxation” stress that decreased with increasing exercise was measured. The amplitude of the “relaxation” and contraction stress was the same for each treatment (F 2,12 = 0.24; p=0.79). Rigor contraction onset coincided with an intra‐muscular pH of 6.6 in each treatment (F 2,12 =0.28, p=0.76). Contraction stress abatement coincided with an “ultimate” pH of 6.2 in each of the treatments (F 1,12 =0.05; p=0.83).