The effects of cold water released from dams on Zacco platypus gonad maturation in the Nakdong River, South Korea

Abstract

Field monitoring was conducted to assess fish gonad maturation and health in relation to water temperature, downstream of the Andong and Imha Dams, South Korea. Throughout the eleven-year survey period (2004–2014), the water temperature immediately downstream of the dam was lower than that at the other survey sites because the temperature of the dam-released water was much lower than that of the natural stream water. Gonad maturation of the fish living downstream of the Andong Dam occurred later than that of fish in the natural streams (Gilan Stream and the control). For instance, Zacco platypus spawning behavior (involving the issuance of eggs and sperm) was not observed downstream of Andong Dam in May, although it was evident in Gilan Stream. In July, toward the end of the spawning season, some spawning individuals were observed in Gilan Stream but none was found downstream of Andong Dam. From the observations, we concluded that when water temperature is not within the suitable range, it negatively affects fish health. Although this has been previously reported in aquaculture, only a few studies have been conducted in natural environments. To ensure sustainability of the Nakdong River downstream of the Andong Dam, suitable river management plans and ecological requirements are proposed based on the results of the present study.