RELATIVE VENTRICULAR WEIGHT OF WILD ATLANTIC SALMON PARR IN RELATION TO SEX, GONAD MATURATION AND MIGRATORY ACTIVITY

Relative ventricular weight (RVW, ventricular weight/body weight . 100 ) was measured for five groups of Atlantic salmon parr from the Girnoc k Burn in Scotland. The mean RVW was: mature males, 0.087; immature re sident males, 0.054; immature resident females, 0.056; immature migran t males, 0.056; immature migrant females, 0.053. For a group of mature male parr from the R. Nith, Galloway, Scotland, the mean RVW was 0.10 8. There were no significant differences in the RVW between groups of immature fish. The RVW of each group of mature male parr was significa ntly greater than those of each group of immature parr. Condition indi ces (weight/length(3)) were closely similar between all groups of parr . The functional significance of plasticity in ventricular weight is d iscussed in relation to life histories of Atlantic salmon.