Analysis of reproductive biological characteristics of Silurus asotus

To study the growth and reproductive characteristics of catfish (Silurus asotus) in the main stream of the Yuanjiang River, and to provide theoretical support for its protection and utilization, we had collected 738 individuals in the Yuanjiang Lingjintan Reservoir area of Changde City, Hunan Province, from May 2018 to April 2020. Then we analyzed the relationship between body length/body mass and reproductive characteristics. The results show a power function relationship between body length and body mass for Yuanjiang S. asotus, with the relationship of W=0.056L^2.57 (R=0.97) and a significant difference  between b-value and theoretical uniform growth value of 3 (P<0.05). The population growth was heteroscedastic, with a population sex ratio of 1.21:1. The average fertility of Yuanjiang S. asotus population was 0.88 (Female: 0.94, male: 0.81, female significantly higher than male, P<0.01). The sexual maturity coefficients of females were higher than those of males (P<0.01) (Female: averagely 7.51, male: averagely 1.85), both highest in May and lowest in September. The annual trends in sexual maturity coefficients for females and males were basically synchronized. The egg diameter reached a maximum of 1626.5 μm in May, gradually decreasing from May to August, which was consistent with the actual peak spawning period. The mean absolute egg mass was 29 677±18 174 and relative egg mass was (107±65) per·g⁻¹. The absolute egg mass was linearly correlated with body mass and length as F=437.36W+945.09 (R²=0.93, P<0.01) and F=1 205.38L−21 285.27 (R²=0.87, P<0.01), respectively. The peak spawning period for Yuanjiang S. asotus was inferred from the annual variation in sexual maturity coefficients to be from mid-May to early August.