Early growth performance of Atlantic salmon full-sib families reared in single family tanks versus in mixed family tanks

The present experiment was designed to assess the impact of the confounding of environmental tank effect with genetic family effect during early rearing periods. In November 1989, two sets of mixed family tanks were created in the Salmon Genetic Research Program (SGRP) hatchery by pooling equal numbers of eggs from four and eight families, respectively. In July 1990, tissue samples and length and weight measurements were collected on fish from both individual family tanks and mixed family tanks. Four polymorphic microsatellites were used to determine unambiguously the family of origin of 790 mixed group fish. There was a strong correlation of family survival rates measured in the mixed tanks and in the single family tanks. Differences among families for length and growth were observed in both the mixed tanks and the single family tanks. However, family growth performance in the single tank environment was poorly correlated with family growth performance in the mixed tank environment and appeared to reflect environmental differences among tanks rather than genetic differences among families. Neither family growth performance in the mixed tanks nor in the single family tanks appeared strongly correlated with subsequent family growth performance up to smolt stage.