DIFFERENCES IN BODY SIZE AND LIPID RESERVES BETWEEN MATURING AND NONMATURING ATLANTIC SALMON PARR, SALMO-SALAR L

Body size and lipid reserves of a group of sibling 0+ salmon parr were monitored monthly from January 1990 until the start of the breeding season in October. Those males that subsequently matured as parr were larger and had a higher fat content than the nonmaturing fish. The size differences were apparent in January and continued throughout the study period. The differences in fat content were apparent in February and continued until October, when the fat content of maturing fish dropped to that of the nonmaturing fish. By the use of logistic regressions basesd on fat reserves and body size it was possible to predict. in late winter, the probability that a male parr would mature in the following autumn. The relative importance of body size and fat content in the maturation process was masked by the strong positive correlation between these two variables.