The histochemistry of muscle in juvenile Atlantic salmon, Salmo solar L.

In fry, 1- and 2-year old juvenile Atlantic salmon, relatively small superficial red muscle fibres staining well for glycogen and succinic dehydrogenase (SDH) but with little myofibrillar ATPase, were evident on either side of the lateral line, in June. Well differentiated relatively large white fibres contained lower concentrations of glycogen than the red fibres, higher ATPase and no SDH, except traces in the larger 1- and 2-year-olds. Intermediate size pink fibres, which were also intermediate between red and white fibres in their staining properties, occurred in a thin diffuse layer along the red-white boundary, thickest at the apex near the vertebral column, and most evident in the younger fish.