Ca2+ handling and oxidative capacity are greatly impaired in swimming muscles of hatchery-reared versus wild Atlantic salmon (Salmo salar)

The swimming capacity of fish is strongly associated with muscle performance, although the prerequisites for effective movements have not been fully described at the molecular level. To compare the condition of swimming musculature of hatchery-reared Atlantic salmon (Salmo salar) with that of wild fish, we analyzed the relative level of two excitation–contraction coupling components (i.e., dihydropyridine receptor (DHPR) and ryanodine receptor (RyR)) and the oxidative capacity of muscles with histochemical and Western blot methods. The density of DHPR and RyR was considerably higher in swimming muscles of wild fingerlings (age 0+) (109.8% and 123.3% in red muscle; 128.6% and 186.0% in white muscle, respectively) and yearlings (age 1+) (153.5% and 459.1% in red muscle; 131.2% and 858.4% in white muscle) as compared with those in reared fish. Similar difference was also observed in the oxidative capacity of muscles. Moreover, the oxidative activity correlated positively with the level of DHPR and RyR. Our data indicate that calcium handling, as well as oxidative capacity of swimming muscles of reared salmon, is clearly separable from the corresponding capacities of wild fish. We suggest that the observed alteration is a major contributing factor to the well-documented differences in swimming ability between wild and hatchery-reared salmon.