Effects of Salinity on the Hatching of the Fertilized Eggs of Epinephelus moara (♀) × Epinephelus lanceolatus (♂) and the Observation of the Morphological Development of Larvae, Juvenile and Young Fish

Abstract:

In this study the hybridization between Epinehelus moara (♀) and Epinehelus lanceolatus (♂) were manipulated in the laboratory. The hybrid F1 larvae were hatched at salinity 30. The hatching and deformity rates of fertilized eggs and the survival activity index of newly hatched larvae was observed at salinities 5, 10, 15, 20, 25, 30, 35, 40, and 45. The growth and morphological characteristics of larvae, juveniles, and young fish was recorded. The results suggested that salinity 35–37 was optimum for the hatching of the hybrid F1, and salinity 20 to 30 was optimum for larval survival. SAI values of larvae became higher when the salinity was between 20 and 35, and they were lower when the salinity was 5, 10, and 45. The post embryonic development could be divided into the larval stage, the juvenile stage and the young fish stage, based on the features of the yolk-sac, the second dorsal fin spine, the pelvic fin spine, the scale and the body color. The embryo developed into pre-larvae in 2 days, and the average length of newly-hatched larvae was (1.959±0.152) mm. This stage was featured by yolk-sac and unabsorbed oil ball. The post-larvae stage lasted from Day 3 to Day 30, and the average length of 3-day larvae was (2.765±0.108) mm. At this stage the absolute length of the second dorsal fin spine and pelvic fin spine reached the maximum for larvae and juvenile fish. It entered into the juvenile stage starting from Day 31 after hatching and the average length was (18.130±1.565) mm. At this stage the visceral organs had been fully developed and the fish color became transparent. Starting from Day 46 after hatching it entered into the young fish stage when the average length was (39.850±2.565) mm and the body color turned light brown. At this stage brown spots appeared on the body surface and scales could be observed under microscope.