Abstract
We induced three types of triploid rainbow trout by retention of the second polar body (RSP) and cross fertilization between tetraploids and diploids (4_??_×2_??_and 2_??_×4_??_) and found that hemoglobin concentration of triploid (4_??_×2_??_) was higher than those of the others. No difference was observed in their hypoxic tolerance between normal two triploids (4_??_×2_??_and 2_??_×4_??_). However, significant differences were observed in the mortalities in bacterial gill disease (BGD) -infected triploids. The tolerance to BGD in triploid (4_??_×2_??_) was higher than those in triploid (RSP) and triploid (2_??_×4_??_). Since it is known that fish with BGD die from asphyxiation and its mortality is affected by the environmental oxygen level, hemoglobin concentration of fish would be closely associated with the tolerance against BGD.
