A comparative study on the age, growth, and mortality of Gobio huanghensis (Luo, Le & Chen, 1977) in the Gansu and Ningxia sections of the upper Yellow River, China.

Abstract

Balkground: Gobio huanghensis is a small economic fish endemic to the Yellow River at the junction of the Tibetan Plateau and the Huangtu Plateau in China. To understand the impact of environmental changes and human activities on the ecological structure of the G. huanghensis population, a comparative study was conducted on the age composition, growth characteristics, mortality rate, and exploitation rate of the G. huanghensis populations in the Gansu and Ningxia sections of the upper Yellow River.

Results: During the investigation, a total of 1147 individuals were collected, with 427 individuals collected from the Gansu section and 720 individuals from the Ningxia section. The results showed that G. huanghensis in the Gansu section exhibited a total length ranging from 5.00 to 22.80 cm, with an average of 12.68 ± 4.03 cm. In the Ningxia section, the total length of G. huanghensis ranged from 2.15 to 20.65 cm, with an average of 9.48 ± 3.56 cm. The age composition of G. huanghensis in the Gansu section ranged from 1 to 7 years, where female fish were observed between 1 and 7 years old, and male fish between 1 and 6 years old. In the Ningxia section, both female and male fish ranged from 1 to 5 years old. The relationships between total length and body weight were (Gansu section, R² = 0.9738) and (Ningxia section, R² = 0.9686), indicating that fish in the Gansu section exhibit positive allometric growth, while fish in the Ningxia section exhibit negative allometric growth. The von Bertalanffy growth equation revealed that G. huanghensis in the Gansu section exhibited an asymptotic total length L_∞ of 27.426 cm with a growth coefficient K of 0.225 yr^-1, while in the Ningxia section, the asymptotic total length L_∞ was 26.945 cm with a growth coefficient K of 0.263 yr^-1. The total mortality rate (Z) values of G. huanghensis were 0.7592 yr and 1.1529 yr in the Gansu section and Ningxia section, respectively. The average natural mortality rate (M), estimated by three different methods, in the Gansu section was 0.4432 yr, while it was 0.5366 yr in the Ningxia section. The exploitation rate (E) of G. huanghensis was 0.4163 in the Gansu section and 0.5345 in the Ningxia section, indicating that the population in the Ningxia section may have been overexploited.

Conclusion: Prolonged fishing pressures and environmental changes may have led to variations in the ecological parameters of the G. huanghensis population between the Gansu and Ningxia sections.