Seventh River Management Branch, WRA, TAIWAN, Taiwan (Republic of China)
Abstract Submission: To realize the impact of the sediment flushing operation on downstream fish community composition, this study uses fish autecology matrix, diversity and evenness index methods to analyze fish, substrate, and water quality data which are collected from 4 sample stations located in the Zengwen River from 1995, 2004 and 2016 to 2022. It can be found that the number of fish caught, the diversity index, and the number of endemic species show a trend of decreasing after flushing and recovering in the next year before flushing. The diversity index of each sample station was higher in 2004 than in 2016 to 2022. It is thought that the sediment replenishment operation may have a negative impact on the fish community. According to the result of the fish autecology matrix, the fish community composition in the Zengwen No.1 Bridge station is affected by flushing and the changes in substrate. The fish community composition in the Mashan Bridge station and the estuary station is not significantly affected by flushing and the changes in substrate and water quality. It is thought that (1) the fish community composition in the Mashan Bridge station and the estuary station prefer fine-grained substrate originally, so the sediment flushing has not affected its composition; (2) it may take time to see the changes in fish community composition resulted by substrate and water quality after flushing; (3) it is considered that the time difference between fish caught and water quality data, and the inconstant water quality may lead to error analysis.
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