Estimates of age, growth, and mortality of Triplophysa pseudoscleroptera in the upstream of the Yellow River, China

Abstract

To investigate the age composition, growth pattern, mortality, and exploitation rate of Triplophysa pseudoscleroptera in the upper reaches of the Yellow River, this study conducted four sampling surveys between 2022 and 2023 to measure the total body length (L) and body weight (W) of a total of 313 individuals. Age determination was performed using otoliths. The collected samples exhibited a total length ranging from 4.50 cm to 13.80 cm, body weight from 0.98 g to 19.38 g, and age range from 1 to 5 years old. The relationship between total length and body weight was described by W=0.0082L2.9392 for all samples, indicating isometric relative growth pattern observed in this study. The von Bertalanffy growth equation revealed that T. pseudoscleroptera had an asymptotic total length L∞ of approximately 18.10 cm with a growth coefficient k estimated as 0.209 yr⁻¹. The exploitation rate (E) is concurrently estimated to be 0.3873. The growth characteristic index of T. pseudoscleroptera is 1.8355; in comparison with other fish species within the same genus, it demonstrates a relatively sluggish overall growth rate. Compared with other Triplophysa fish, the growth rate of T. pseudoscleroptera in the upper reaches of the Yellow River appears to be relatively slow, and its mortality rate is predominantly influenced by fishing activities. Therefore, given the relatively high fishing mortality rate and the current situation in the Yellow River for T. pseudoscleroptera, it is imperative to implement locally tailored management strategies to safeguard the population of this species. These strategies should include measures to regulate the introduction of nonindigenous fish and establish regulations on the utilization of finer mesh fishing tools owing to their more obvious detrimental impact on small and medium-sized fish.