Survival rates between the ¢rst feeding and 200
days is presented in Figs1and 2.Very highmortalities
were observed in diploid and heat-shocked triploid
hybrid groups between the ¢rst feeding and the 20th
day. Triploid rainbow trout groups had also demonstrated
high mortality during this period. Survival
rates of control hybrids were higher than for triploids
in days 20,40 and 60 but di¡erences were not signi¢-
cant. During this period, from the ¢rst feeding to the
60th day, heat-shocked hybrid mortality was higher
than for control hybrids. In later periods, betweenthe
140th and the 200th day, viability of heat-shocked
hybrids was higher than for non-shock-induced control
hybrids.