Performances of auto and allotriploids in salmonids I. Survival and growth in fresh water farming

Survival and growth performances of autotriploids in rainbow trout (Salmo gairdneri) and three types of triploid hybrids between female rainbow trout and brown trout males (Salmo trutta,) coho salmon males (Oncorhynchus kisutch) and brook trout males (Salvelinus fontinalis) were analysed relatively to the parental species in freshwater farming conditions. At the end of the immature period, autotriploids exhibit moderate but significant depression relative to the control for both survival (about 25% depression) and growth (10 to 15% depression). Most of this depression is established during the first three months of life, triploids appearing very similar to the control later on. At the onset of sexual maturation at 2 years old, relative value of triploids becomes higher than that of the control, for both survival and growth. Long term evaluation (2+ or 3+) balances in favor of triploids with particular advantage for triploid females. Triploid hybrids exhibit much more important depression in early survival (up to 60%). Later on, their survival remains always lower than those of parental controls. Their growth performances are intermediate between their two parental species. Despite a relative advantage for these groups during the onset of sexual maturation in control groups, especially for growth, long tem evaluation is in favor of diploid rainbow trout, but in some specific cases.