HOW SHOULD ENZYME-ACTIVITIES BE USED IN FISH GROWTH-STUDIES

The activity of glycolytic and oxidative enzymes was monitored in the white muscle of Atlantic cod Gadus morhua experiencing different growt h rates. A strong positive relationship between the activity of two gl ycolytic enzymes and individual growth rate was observed regardless of whether the enzyme activity was expressed as units per gram wet mass, units per gram dry mass or with respect to muscle protein and DNA con tent. The most sensitive response to growth rate was observed when pyr uvate kinase and lactate dehydrogenase activities were expressed as un its per microgram DNA, and this may be useful as an indicator of growt h rate in wild fish. In contrast, no relationship between the activiti es of oxidative enzymes and growth rate was observed when cytochrome c oxidase and citrate synthase activities were expressed as units per g ram protein, Apparently, the aerobic capacity of white muscle in cod i s not specifically increased to match growth rate.