Estimating population abundance and utilization of Rhinogobio ventralis, an endemic fish species in the upper Yangtze River

Abstract

Rhinogobio ventralis, an endemic species in the upper Yangtze River, has been threatened by overfishing and dam construction. To understand its population dynamics after the Three Gorges Reservoir was built and before the Xiangjiaba and Xiluodu reservoirs were built, we employed body length-frequency data to estimate growth and mortality parameters, population abundance and utilization of the fish based on surveys in the Jiangjin and Yibin sections of the upper Yangtze River conducted from 2007-2009. Fish ranged from 52 to 250 mm in length and 2.7 to 307.2 g in weight, with an average length of 150.8 ± 40.7 mm and an average weight of 72.3 ± 49.7 g. The average size of the fish in the Jiangjin section of the Yangtze River (168.6 ± 29.5 mm) was significantly larger than that in Yibin section (125.6 ± 41.2 mm). The length-weight relationship of R. ventralis was well-fit with a power function, W = 6.06 × 10 P < 0.01, n = 436). Asymptotic length (L∞) and growth constant (k) were estimated using length frequency data as 338 mm and 0.24/yr, respectively. Average natural mortality was comprehensively estimated as 0.43 using three empirical formulas proposed by Pauly, Gunderson & Dygert, and Jensen, respectively. The total mortalities were estimated using a length-converted catch curve analysis as 2.26 in the Jiangjin section and 2.09 in the Yibin section of the Yangtze River. The observed exploitation rates were 0.81 in the Jiangjin sec- tion and 0.79 in the Yibin section, which were higher than the maximum exploitation rates of 0.57 in the Ji- ·研究报告·