Comparison of survival rate, growth and response to transport stress in diploid, triploid and tetraploid rainbow trout Oncorhynchus mykiss (Walbaum, 1792)

The aim of this study was to assess the effects of triploidy and tetraploidy induction on survival, growth performance and response to transport stress in rainbow trout (O. mykiss) fry (with a weight range of 2-2.5g). To this purpose, 8 female (1600±246 g) and 6 male (1393±186 g) rainbow trout broodstock with the mean age of 4 years were used. Ten min. after insemination, the eggs were subjected to heat-shock for 10 min. submerged in a 28 °C water bath to induce triploidy. Tetraploidy was also induced by a thermal shock at 65 hour-degrees after fertilization in a 28 °C water bath for 10 min. Based on measuring area and volume of red blood cells, the overall triploidization and tetraploidization success level was 87.1±1% and 68.21±2%, respectively. Survival rate from fertilization to eyed stage in triploids (86.31 ± 1.21%) was significantly lower than that in diploids (92.12± 1.59%). Survival rate from eyed stage to hatching in triploids (94.04 ± 1.33%) was also significantly lesser than that in diploids (98.10 ± 0.45%). Survival rates of tetraploids in the three stages were significantly lower than those of the other experimental groups. After transportation stress, cortisol concentration in triploid fish (67.33 ± 4.48 ng/ml) was higher than that in other groups. The results showed that both triploidy and tetraploidy induction can lead to decreased survival rate. Moreover, the survival rate and physiological response of tetraploid fish to transportation stress is different from triploids but almost similar to diploids.