A snapshot sample of Arctic charr (Salvelinus alpinus) from Heintzelman Lake (81‹42ŒN, 66‹56ŒW), Ellesmere
Island, Canada was used to elucidate the biological and life-history factors potentially influencing individual
total mercury (THg) concentrations. Migratory history was significant, with anadromous fish having a lower
mean THg concentration (64 ƒÊg/kg ww) than the non-anadromous Arctic charr (117 ƒÊg/kg ww). The increase
in individual THg concentration with age was shown to be independent of length-at-age when large
and small individuals within the same age groups were compared. Similarly, the diets of individual Arctic
charr were comparable regardless of size, and there was no apparent ontogenetic shift in diet that could explain
differences in length-at-age or THg concentration among fast- and slow-growing groups of fish (i.e., fish
of the same age but differing sizes). Maturity state was also not related to THg concentration, but appears to
be related to differences in length-at-age, with slow-growing fish allocating more energy to reproduction
than fast-growing conspecifics. The differences in THg concentration among individual Arctic charr were
best explained by fish age. We suggest that the increase in mercury concentration with age can be altered
by a shift in diet (e.g., to piscivory) or habitat (e.g., anadromy), but is otherwise unaffected by changes in
size or length-at-age.