Study on Individual Fecundity of <i>Hemibarbus medius</i> in Beiliu River

Fish individual fecundity is an important factor governing fish replenishment and population dynamics. An in-depth understanding of the dynamics of fish fecundity is not only important for the study of fish and fisheries ecology but also of great practical significance. From mid-February to early March 2023, we collected 99 samples of Hemibarbus medius in the Beiliu River and analyzed their body length, body weight, empty shell weight, and gonadal weight. Using the weighing mass method, we calculated the absolute fecundity of each individual, relative fecundity in terms of the body length and weight, gonadosomatic index, and Fulton’s condition factor. We used six mathematical models to fit the relationship between individual fecundity and the biological indicators of H. medius . The study demonstrated that the female-to-male ratio in the samples was 1.06:1, and the minimum age for sexual maturity was observed as 1 + and 0 + years old for females and males, respectively. Furthermore, the body lengths of females with gonadal development of stage IV or above ranged from 11.5 to 25.7 cm, while their body weights ranged from 24.04 to 263.42 g. The absolute fecundity of individuals varied significantly, ranging from 195 to 14,044 eggs. The relative fecundity of the lengths was between 17 to 624 eggs/cm, while the relative fecundity of the body weights ranged from 5 to 76 eggs/g. This study established that absolute fecundity exhibits power function correlations with various biological indicators except for parabolic correlation with Fulton’s condition factor of H. medius , whereas body length relative fecundity demonstrates power function correlations with all biological indicators except parabolic correlations with empty shell weight and Fulton’s condition factor. Notably, body weight relative fecundity displays significant correlations only with the gonadosomatic index. These findings are crucial in accurately estimating the population size of H. medius in Beiliu River and its change pattern. In addition, these findings provide a foundation for resource management and rational utilization of H. medius in the Beaulieu River.