Early Life History Variation among Hatchery- and Wild-Origin Lake Trout Reared in a Hatchery Environment

Hatcheries play a key role in augmenting populations for conservation, harvest, or both, although rapid domestication and adaptation to hatchery conditions may lead to fish that are maladapted to natural environments. Three processes may lead to domestication: (1) negative selection against fish adapted to wild environments, (2) positive selection for fish that thrive in artificial conditions, or (3) relaxation of selection pressures. In this study, early life history traits and survival were contrasted among wild- and hatchery-origin lake trout Salvelinus namaycush reared in a common hatchery environment to address the hypotheses of processes leading to domestication. Examination of egg size, egg survival, fry deformity, and early growth rate found no evidence of negative selection against wild- origin lake trout or positive selection for hatchery-origin lake trout when reared in a hatchery environment. Wild-origin lake trout outperformed hatchery-origin fish in all life history traits examined, suggesting that relaxation of natural selective pressures may be occurring in the hatchery environment. Furthermore, the hatchery-origin strains failed to show maternal effects on egg size and exhibited limited variability in egg size and hatching time, as well as no significant differences in early growth rate, suggesting potential homogenization of life history traits as a result of the hatchery environment.