Production of sterile trout (Triploids) by chromosome set manipulation using thermal shock treatment in rainbow trout (Oncorhynchus mykiss) from Kashmir Himalaya

Rainbow trout is one of the promising cultivable fish species and has wide potential for its expansion. Being a low volume, high value commodity the trout has strong potential for both domestic consumption and international export. It is a cold water fish belonging to the family Salmonidae and requires an optimum temperature range of 10–15℃ for best growth. The current study to produce sterile trout (triploids) using thermal shock treatment in ( O.mykiss ) was carried out at the government trout farm Laribal, Srinagar. Heat shock at 26 o C and 28 o C for 10 min. duration were applied 15 min. and 20 min. after fertilization using a water bath. No treatment (heat shock) was given to Control. The highest fertilization rate (90.393 ± 0.37%) was observed in group T1, heat shocked at 26 o C, after 15 minutes of fertilization (TAF) for 10 minutes. The highest hatching rate (81.843 ± 0.88%) among the treatment groups was observed in group T2, heat shocked at 26 o C for 10 minutes after 20 minutes of fertilization. The highest yolk sac absorption rates for treatment groups was observed in T2 (83.94 ± 0.52%) heat shocked at 26 o C, after 20 minutes of fertilization (TAF) for 10 minutes. T4 group showed the highest triploidy rate of 76.66 ± 3.33% heat shocked at 28 o C, after 20 minutes of fertilization (TAF) for 10 minutes. However, no triploids were observed in control group. It is observed that temperature intensity showed significant negative correlation with fertilization rate and hatching rate (r= -0.168, p < 0.01; r= -0.492, p < 0.01) respectively. However, fertilization rates displayed significant negative (r= -0.378, p < 0.01) and hatching rates showed significant positive correlation with heat shock time after fertilization (r = 0.624, p < 0.01) respectively. Yolk sac absorption rate and triploidy rates showed significant positive correlation with heat shock time after fertilization (r = 0.778, p < 0.01; r = 0.382, p < 0.01) respectively. However, temperature intensity formed significant negative correlation with yolk sac absorption rates (r= -0.556, p < 0.01) while as significant positive correlation was observed between temperature intensity and triploidy rates (r = 0.891, p < 0.01).Control group showed higher survival rates at fertilization (93.16 ± 0.41%), hatching (84.28 ± 0.46) and at complete yolk sac absorption (86.27 ± 0.55%) compared to heat shocked groups.