Effects of various temperature-salinity conditions on post embryonic-hatching process of saffron cod (Eleginus gracilis)
2018
Chen, A.L. | Yoshida, H. | Sakurai, Y.
The post embryonic-hatching process of saffron cod Eleginus gracilis was examined at 28 different temperature-salinity conditions ranging from -1.3 to 3.3degC and from 10 to 33permille. Our results indicate that the relationship between temperature and the number of days to 50% hatching was exponential. The hatching process observed at constant conditions (< 0degC, 32-35permille) as well as increasing temperatures (1.3-3.3degC) or decreasing salinities (10-20permille) indicate that the advanced developmental stages were acclimated to higher temperatures rather than salinity dilution. Complete yolk absorption of hatched larva occurred within 19 days at 1degC and 13 days at 3degC. Artificially fertilized eggs incubated in suspended basket and transplantation in Lake Saroma, developed up to stage IV-V in 43-51 days in the beginning of March, and up to stage V in 66 days by late March. Natural water temperature gradually increased from below zero and abruptly reached around 3degC in the middle of April. Their normal hatching period was supposed to 80 to 100 days. Laboratory analysis and field results indicate that increase in water temperature triggers early hatching of saffron cod and occurs simultaneously with melting of ice.
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