Post-mortem calorimetric and biochemical profiles of Chinook salmon (Oncorhynchus tshawytscha) white muscle following rested and exhausted harvesting

We report calorimetric and biochemical profiles of anoxic, post-mortem, white muscle from Chinook salmon subjected to rested and exhausted harvesting regimens. Heat output was greater (P < 0.01) in the rested group immediately after death (ca. 400 μW g−1), and for the first 7 h post-mortem, reaching a nadir of about 15 μW g−1 by 12 h. In exhausted animals, heat output was relatively unchanged at <10 μW g−1 over 24 h. In both groups there was an exothermic event, occurring between 4 and 6 h post-mortem, amounting to a rise of ca. 35 μW g−1. The greater heat production by the muscle from rested animals was accompanied by elevated pH (7.5 vs 6.7, P < 0.05), and higher concentrations of glycogen (16 vs 2 μmol g−1), creatine phosphate (18 vs 0.1 μmol g−1), ATP (6 vs 3.5 μmol g−1) and potential energy (30 vs 7 μmol g−1) than the exhausted group, which had elevated concentrations of lactate (43 vs 18 μmol g−1, P < 0.05) and glucose (5 vs 2 μmol g−1), over a number of hours post-mortem. The maintenance of potential energy in the form of ATP, glycogen and creatine phosphate for an extended period post-mortem indicates that tissue viability is extended in muscle from fish that are harvested in a rested manner.