Post-Mortem Glycolytic and Associated Changes in the Muscle of Trap- and Trawl-Caught Cod

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Abstract
Glycolytic activity in the muscle of heavily-feeding trap-caught cod (Gadus morhua) during the struggle involved in catching, and the subsequent post-mortem changes during holding in ice and at ambient temperatures were investigated. Struggling of the fish in the trap and during boating was sufficient to cause a partial depletion of the muscle energy reserves, as indicated by lactate production and nucleotide dephosphorylation and deamination. One cod from the trap, boated and killed without apparent struggling, had a high initial glycogen content of 550 mg/100 g. During subsequent storage of the brailed fish in air or ice the glycolytic processes, including nucleotide degradation, continued, although during the early post-mortem period the rate of lactate production greatly exceeded that of glycogen depletion. Little change in concentration of the metabolites occurred on freezing and storage at −26 °C for 4–6 weeks. In contrast, trawled offshore cod and haddock, regardless of ante-mortem treatment, contained little or no glycogen; almost complete dephosphorylation and deamination of the nucleotide compounds had occurred during the struggle involved in catching. Therefore, at the time of boating, the energy reserves in the trawled fish have been exhausted or nearly so.