Population characteristics and resource status of Coreius heterodon in the Yichang section in the middle reaches of the Yangtze River

To understand the population characteristics and resource changes of Coreius heterodon in the Yichang section in the middle reaches of the Yangtze River after impoundment of the Three Gorges Reservoir, population parameters and resource status of C. heterodon were analyzed using FISAT Ⅱ software based on the biological data obtained from gillnets deployed in the Yichang section during 2003−2005, 2009−2011 and 2017−2021. Results showed that body length ranges were 118-416 mm, 111-409 mm and 107-380 mm, and weight ranges were 10-1000g, 19-889 g and 16-816 g, respectively. Average body lengths and weights of C. heterodon in the three periods were (230.7±49.8) mm, (217.5±54.3) mm, (267.2±34.1) mm, (195.8±123.6) g, (153.2±118.6) g and (250.3±84.2) g, respectively. Growth indices (b) were 3.015, 3.032 and 2.978, respectively, which belonged to the uniform growth type. The asymptotic length (L_∞) of C. heterodon was 535 mm in 2003-2005, 530 mm in 2009-2011 and 500 mm in 2017-2019, respectively, with growth coefficients (k) at 0.18, 0.14 and 0.15. According to the length-structured virtual population, annual population of C. heterodon were estimated to be 1.10×10⁶, 1.89×10⁶ and 2.10×10⁶, respectively. After the impoundment of the Three Gorges Reservoir, although the C. heterodon in the Yichang section grew at a uniform rate, and the resource increased significantly, the growth rate slowed down and showed a trend of miniaturization. Results in this paper would provide scientific basis for the protection and utilization of fishery resources in the middle reaches of the Yangtze River after the moratorium.