Application of environmental DNA technology in natural reproduction of the four major Chinese carps in Yichang section of Yangtzi River, China

Abstract

We explored the sample collection and DNA extraction method of environmental DNA (eDNA) technique. Droplet digital PCR (ddPCR) was used to detect the eDNA concentration of the four major Chinese carps in different water layers and different cross-sections of Yichang section of Yangtze River trunk stream. We analyzed the relationship between eDNA concentration and density of egg and fry, and explored the feasibility of using eDNA technique to monitor the natural reproduction of the four major Chinese carps. Compared with the results from traditional survey methods, the eDNA concentration of the four major Chinese carps was extremely significantly correlated with egg and fry density. The maximum concentration was consistent with the peak occurrence time of egg and fry, suggesting that eDNA technique could predict the fishcrowd behavior for spawning. The investigation of cross-section eDNA concentration during two consecutive years suggested that the range of fish spawning ground was 4.5 km upstream to 1 km downstream of Yuyangxi. The predicted spawning ground was located within the range estimated by traditional methods from the lower part of Carmine Dam to Honghua Tuo. Our results indicate that eDNA technique, as a new ecological investigation method, could more accurately determine the distribution of fish with a certain population size, and thus with a good application prospect.