Embryonic development and sensitive stages of Atlantic salmon (Salmo salar) eggs

The normal embryonic development of Atlantic salmon eggs was described and illustrated from fertilization to hatching. Additionally, sensitivity based on acute mortality 7 days after mechanical stress exposure was recorded from fertilization to hatching. A mechanical shock device was used for the mechanical stress test, where eggs were dropped from different predetermined heights, and the heights corresponding to 10% and 50% mortality were estimated (LD10 and LD50). The sensitivity was observed to increase from fertilization until gastrulation, where maximum sensitivity occurred, before decreasing throughout late gastrulation and until the "eyed" stage where no mortality was observed at any height. This information may be important for hatchery managers in the decision-making process regarding optimal handling routines.