Temporal changes in tissue metabolic capacities of wild Atlantic cod Gadus morhua (L.), from Newfoundland

We used biochemical indicators to assess the physiological status of Atlantic cod (Gadus morhua) sampled at different sites and times along the Newfoundland coast. The physiological status of cod changed more with time of sampling and size of the cod than with the site of sampling. The levels of muscle glycolytic enzymes and proteins suggest that cod from both near shore and offshore environments experienced the most favorable conditions in late summer and early fall. In small cod sampled near shore, increases in muscle aerobic capacity and protein contents accompanied the decrease in temperature from September to December. The positive allometry of muscle glycolytic capacities was more apparent in samples obtained in early winter than at other times, suggesting that the energetic status of cod affects the expression of this allometric relationship. On the other hand, a negative allometry of muscle aerobic capacities was apparent throughout the study. Reproductive maturity had few effects upon the biochemical parameters measured and tended to favor mature over immature cod. Our results suggest that cod in these areas were only growing in fall.