The ovarian condition is divided into 6 maturation stages according to the morphologic character of the ovary, gonadosomatic index (GSI), ova diameter (OD), and ova structure. In the lst stage, the OD is 0.005 - 0.014 mm. The sex cannot be distinguished by the eyes. In the 2nd stage, the GSI is 2.9×10^-3 - 10.2×10^-3. OD is 0.007 – 0.490 mm, but the ova can be hardly seen by the eyes. In the 3rd stage, there can be seen blood vessel and ova on the ‘surface of the ovary. GSI is in 15.2×10^-3 - 81.9×10^-3, OD is 0.175 - 0.950 mm. In the 4th stage, there can be easily seen with the eyes the big of little ova on the surface of ovary. The GSI is 78.0×10^-3 - 230.0×10^-3, OD is 0.300 - 1.475 mm. In the 5th stage, there can be seen many matured ova in the ovary. The GSI is 117.2×10^-3 - 393.2×10^-3, OD is 0.315 - 2.030 mm. In the 6th stage, there are no big ova in the ovary. The ovary color is changed to the redness of the skin. The GSI is 51.4×10^-3 - 89.3×10^-3, OD is 0.350 - 1.250mm.

The yearly gonadic is divided into 4 phases, i.e. development from March to April, maturation from May to June, spawning from July to August, and convalescence from September to February of the next year. The spawning period is from May to July and the peak period is from middle of May to middle of June. The spawning period in the north is later than that in the south.

The matured age is moved up because of increasing fishing effort, and is 2 years lod after, and one year old before, the 70’ s. The minimum matured fork length and body weight are 395 mm and 495 g for females and 360 mm and 355 g for males.

The sex radio is 50.2 : 49.8. Female are more than males among 3 years old individuals and during the spawning period, and males are more than females among 2 years old individuals and during the wintering period.