The hatching jar should be circular with a diameter of 40 cm and 50 1 capacity. A hatching jar of this capacity can hold about 50 000–100 000 eggs. If not available, fibre-glass tanks of the same sizes can be used.
Fertilized eggs should be treated with 5 ppm of acriflavine solution for one minute or in ovadine at dilution of 1 cc per 100 cc water. Since egg survival and disinfectant activity are highest at neutrality, an adjustment of disinfectant solutions to pH 7.0 is necessary. After disinfecting, wash the eggs 2 to 3 times before placing in the hatching jar. Hatching rates of seabass eggs vary with salinity (Table 3). The recommended best salinity range is between 20 and 30 ppt.
During the hatching process, aeration should be given gently in 3–5 spots to allow the water to circulate and prevent the eggs from accumulating on the bottom. The seabass egg is buoyant. The unfertilized eggs can be separated by stopping the aeration so that fertilized eggs will float to the surface.
After the 10th hour, half the water should be changed by siphoning out the lower layer. It should be kept in mind that the salinity of the new seawater should be the same as the original water (28-30 ppt).
After about 17.5 hours, the eggs will hatch. The stage of development of the seabass egg recorded by Maneewongsa and Tattanon (1982a) is given in Table 4 and Fig. 2. The newly hatched larvae (size about 1.5 mm) contain a big yolk sac with an oil drop at the anterior end. When it does not swim the fish has its head in an upward position. While moving, the body of the fish will be at a 45-90 degree angle with the horizontal. The body is slender and compressed. The pigment is scattered in spots. The eye, digestive system and intestines can be seen clearly. The mouth parts appear when the fish is three days old. The yolk sac is absorbed when the fry attain four days. If possible the fry should be reared in a running seawater system to ensure good water quality.
