Metabolic organization in swimming muscle of anadromous coregonines from James and Hudson bays
The metabolic organization of swimming muscles from anadromous cisco (Coregonus artedii) and lake whitefish (Coregonus clupeaformis) sampled in two rivers presenting different regimes of migratory difficulty and temperature was compared. Cisco muscle showed an increased aerobic capacity in the river where the fishes' migration is longer, as shown by the activities of several enzymes and by the proportion of red muscle in their swimming muscle. Lake whitefish, generally larger than cisco, did not show any compensation for the difficulty of migration. For both species, latitudinal differences in thermal regime were not correlated with differences in aerobic capacity. As estimated from published allometric equations, scaling effects can account for only a small proportion of the interstation variation in the aerobic enzyme activities of cisco. Our results suggest that because cisco are smaller than lake whitefish in these rivers, and thus are more affected by the degree of difficulty of the prereproductive migration at a given temperature, cisco have compensated by increasing the aerobic capacity of their swimming musculature in populations facing greater swimming requirements.