AGE AND GROWTH CHARACTERISTICS OF COILIA NASUS IN THE THREE GORGES RESERVOIR REGION

Coilia nasus is one of the anchovy species that exclusively lives in freshwater environments, which has been increasing, and its distribution range has been gradually expanding in the Three Gorges Reservoir Region since it was first identified in 2015. Up to now, there was still no research on the resource status, ecological effects, adaptation strategies, and risk assessments concerning Coilia nasus in the Three Gorges Reservoir Region. In order to investigate age and growth characteristics of Coilia nasus in the Three Gorges Reservoir Region, 459 individuals were collected from Penxi River, Meixi River, Caotang River and Daning River from July to December 2019. The results showed that the age of Coilia nasus ranged from 1 to 6, and sexual maturity was reached at the age of 1. The proportion of individuals aged from 1 to 3 years old was 90.85%. The average body length and average weight of sampled individuals were (16.57±0.21) cm (mean±SE) and (19.14±0.78) g (mean±SE), respectively. The relationship between body weight and body length could be expressed as W=0.0038L^2.957(R²=0.987). The Von-Bertalanffy growth equations of female and male Coilia nasus were L_t=38.5671–e^{–0.196(t+0.985)}, W_t=183.0291–e^{–0.196(t+0.985)2.938} (♀) and L_t=34.7111–e^{–0.26(t+0.603)}, W_t=143.5991–e^{–0.26(t+0.603)2.995} (♂), respectively. The growth inflection points of body weight were 4.62 (♀) and 3.62 (♂). Moreover, these results indicated that Coilia nasus from the Three Gorges Reservoir Region belonged to a small individual population, which had simple age structure, upward trend in population number, high proportion of females, and abundant reproductive potential. Therefore, in order to protect the safety and stability of the aquatic ecosystem, further studies on the influences and risk assessments of Coilia nasus on the aquatic ecosystem of the Three Gorges Reservoir Region should be carried out.