Ovulation and egg survival following exposure of Atlantic salmon, Salmo salar L., broodstock to different water temperatures

Abstract The timing of ovulation and survival of eggs following exposure of 2-sea-winter Atlantic salmon, Salmo salar L., to different temperature regimes during the spawning season were investigated. Water temperature was either increased from 10 to 13–14°C (warm water), decreased abruptly from 10 to 5–7°C (cold water), or gradually decreased from 10 to 8°C (ambient control) from 1 November onwards. Median ovulation time was delayed by 5 weeks in the warmwater group compared with ambient controls, with 43% of the females remaining non-ovulated at the end of the study. Only minor effects were observed on timing of ovulation in the coldwater group compared with ambient controls. Survival of eggs to the eyed stage was significantly higher in the coldwater group (92·1%), compared with both the ambient control group (84·5%) and the warmwater group (76·6%). The results indicate that high water temperature during the spawning season inhibits ovulation and has a detrimental effect on gamete quality in Atlantic salmon.