Survival rates associated with in vitro low-temperature storage of kutum (Rutilus kutum) eggs

To study the effects of post-stripping oocyte ageing at low temperatures on the viability of kutum (Rutilus kutum) oocytes, unfertilised eggs of five females were stored in ovarian fluid at temperatures of 4 and 7 degree centigrade for 24 hours post stripping (HPS). The stored ova of five female kutum were separately fertilised at 0 (i.e., control eggs fertilised prior to storage), 4, 8, 12, 16, 20, and 24 HPS. The eyeing and hatching rates were recorded as indices of the egg quality. The results indicated that the maximum eyeing and hatching rates of the eggs (92% and 74%, respectively) were observed at 0 HPS, whereas the storage of the eggs at 4 °C for 24 HPS decreased the eyeing and hatching rates to 36% and 28%, respectively. The use of the higher storage temperature resulted in a more rapid decrease in the egg viability: eyeing and hatching rates of 9% and 2%, respectively, were obtained after storage at 7 °C for 24 HPS. The present study demonstrated that stripped kutum eggs that are stored in ovarian fluid at 4 and 7 degree centigrade should be fertilised within 12 and 8 HPS, respectively, to obtain viability rates higher than 50%.