| Summary: | 碩士 === 國立海洋大學 === 海洋生物研究所 === 90 === The purpose of the study is to understand the effect of thermal seawater discharges on the community structure, diet and mortality of fishes in the waters around the second nuclear power plant in Taiwan. The fishes were sampled from the three different habitats, sand-muddy bottom and rocky habitats and estuarine, which have different distances from the thermal seawater discharges. For the community structure, we use ANOSIM (Analysis of similarities), Cluster and Ordination methods to analyze the spatial and temporal variation of community structure. For the fish diet, we use stomach contents observance (IRI value) and stable isotope (δ13C and δ15N) to understand the spatial variation of fish diet. The results show that the community structure showed temporal variations in the three different habitats. The community structure and diet of the fishes from the sand-muddy bottom showed on significant difference among different stations. It seems that there is no effect on the sand-muddy bottom fishes by the thermal seawater discharge. For the fishes in the rocky habitats the community structure during summer and diet showed significant difference among different stations and suppose the effect of the thermal seawater discharges. We suppose that different tolerance of water temperatures of fish caused different species compositions among different stations within the rocky habitats or the changes on the species compositions of prey by thermal seawater discharge may influence on the distribution of stenophagous fishes. For the fishes in the estuarine, the community structure and diet showed significant difference among stations. However, the microhabitats are different between stations. Hence, the differences in the community structure or diet should be the result of different microhabitats. We estimated the mortality of fishes from length frequency analysis (LFA) (use FISAT program), and the result show that there is the highest mortality of fishes in the station nearest the thermal seawater discharge, the higher water temperature may be the reason of high mortality in this station. We use Jaccard index to analysis the similarity of community structure among three different habitats fishes, and the result shows that the species compositions are different. Therefore, this study has collected fishes around second the nuclear power plant as completely as possible. The conclusion is that there is no effect on the fishes from the sand-muddy bottom by the thermal seawater discharge of the second nuclear power plant, but the community structure during summer and diet of fishes in rocky habitats are influence by the thermal effect. In addition, the increase mortality of fishes in the station nearest the thermal seawater discharge may be caused by higher water temperature.
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