Objective This study aimed to investigate the effects of different salinity conditions on the hatching rate, hatching time, egg diameter, oil globule diameter, and size of newly hatched larvae of Acanthopagrus berda, in order to determine the suitable salinity range for hatching and provide a theoretical basis for artificial breeding research.

Methods The experiment was set up with 8 salinity gradients (salinity 0-35), with salinity 30 as the control group, and three replicates were set for each group. The hatching status and hatching time of fertilized eggs were observed at room temperature, and the number of newly hatched larvae was counted. Samples were taken from each group at 5, 10, 20, 30, 50 70, 90, and 120 min, and then every hour after 2 hours. Hatching was observed under a microscope, and measurements were taken for egg diameter, oil globule diameter, and the size of newly hatched larvae. One-way ANOVA was used to compare the significant differences among different salinity groups.

Results The fertilized eggs of the A.berda can hatch within a salinity range of 10-35. No hatching occurred at salinities of 0 and 5, while the lowest hatching rate was observed at salinity 35. The highest hatching rate was observed at a salinity of 20‰. Within the salinity range of 15‰ to 25‰, hatching rates remained relatively stable, all above 56%, which can be considered a suitable salinity range for hatching. By fitting the relationship between hatching rate and salinity with a quadratic equation, the optimal salinity for hatching within the suitable range is found to be 18.47. In addition, the egg diameter of A.berda decreased with increasing salinity, whereas the oil globule diameter unchanged with salinity or time. Calculations using a polynomial regression equation indicated that the total length of newly hatched larvae reached its maximum at around a salinity of 19.8, showing a trend of first increasing and then decreasing within the suitable hatching range.

Conclusion The study showed that salinity is a key environmental factor affecting the hatching process (hatching rate and hatching duration) of A.berda fertilized eggs and the size of newly hatched larvae. Experiments have determined the suitable salinity range and the theoretical optimal salinity value for the hatching of A.berda fertilized eggs, providing a theoretical reference for the technical optimization of its artificial breeding.