Chemical water quality and fish component analyses in the periods of before- and after-the weir constructions in Yeongsan River

Abstract

The objective of this study was to analyze chemical water quality, ecological characteristics of fish compositions, and ecosystem health before- (Bwc; 2008-2009) and after-the weir construction (Awc; 2011-2012) at Juksan Weir and Seungchon Weir of Yeongsan River watershed. Suspended solids (SS) and chlorophyll-a (Chl-a) in Juksan Weir increased, where­as nutrients such as total nitrogen (TN) and total phosphorus (TP) decreased in the epilimnetic water. In Juksan and Seungchon weirs, fish species distribution analysis in the periods of Bwc and Awc showed that sensitive species were rare and tolerant species were dominant in the community. In the analysis of trophic guild, relative abundance of carnivore species are increased to 22% and 12%, respectively, after the constructions of Seungchon Weir and Juksan Weir. Mann- Whitney U-tests of nonparametric statistical analysis indicated that omnivore and carnivore species had significant dif­ferences (p < 0.05) between the Bwc and Awc. The massive population growth of an exotic species, Micropterus salmoides, was evident in Seungchon Weir to influence on the structures of fish communities. The model values of mean Index of Biological Integrity (IBI), based on fish assemblages, were < 15, which indicates "poor” condition in the river health, and the significant difference of IBI values was not found between the Bwc and Awc.