Circulating levels of the steroid hormones 11-ketotestosterone (11-KT) and
17 beta-estradiol (E2), voluntary food intake, and growth performance were
measured in individual Atlantic salmon (Salmo salar) over the year precedin
g their maturation as grilse. 11-KT and E2 were measured by radioimmunoassa
y, and X-radiography was used to measure food consumption rates. Two phases
of sexual maturation were identified: the early phase (October 1992 - Apri
l 1993) was characterized by slowly rising steroid hormone levels concomita
nt with relatively high rates of food consumption and growth, and in the la
te phase (May-October 1993), steroid hormone levels increased more rapidly
and growth rates decreased in association with inappetence. Significant lin
ear relationships were observed between food consumption and specific growt
h rates of fish throughout the study (ANCOVA, p < 0.05). Slopes and interce
pts of regressions were similar for fish during early maturation, while a l
ower intercept and steeper slope (ANCOVA, p < 0.05) was observed during the
later stages of maturation. In November, January, February, and April, fis
h in which steroid hormone levels were elevated were significantly heavier
than those in which hormone levels were basal. There were no significant di
fferences in specific growth rates (except in February), food consumption,
or weight-specific food conversion ratio (except in August and October) ass
ociated with maturation status.