| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋生物研究所 === 98 === Habitat destruction and habitat fragmentation is one of the main causes that downgrade marine biodiversity. In Taiwan, more than half of its total natural coastal lines have been changed to artificial coastal lines by way of ports constructions and jetty and breakwater installations. These structures have made the ratio of Taiwan’s artificial coastlines the highest of the world. How serious the effects are of these concrete coastlines on fish assemblages have never been fully investigated. For this reason, we chose 7 artificial coastal sites in northeastern Taiwan (Nanya, Bitou, Longtung, Jinsahwan, Meiyenshan, Fulong, and Maoao) and nearby natural reefs (20-50 m apart) to conduct underwater visual census with 3 replicates at each site (< 2m water depth). These census were repeated 3 times from May to July 2007 for a total of 9 observations at each site. For all 7 sites together, 95 species in 28 families were recorded from the natural reefs and 41 species in 17 families were recorded from the artificial coastlines. Whether it is the number of species or the number of fishes at the 7 sites, the richness of fish in the natural reefs are all significantly higher than that of the artificial reefs. The result from the multivariate statistical analysis using ordination (MDS) and the clustering analysis (Bray-Curtis Index of Similarity) also show a significant difference between the two kinds of habitats (R2=0.821). This difference is not affected by the substratum types surrounding these two different habitats, nor is it affected by the possible difference of micro-habitat or geographical differences among these 7 sites (R2=0.324). Among those dominate species, the species of Pomacentrus coelestis, A. bengalensis, Stegastes fasciolatus, Stethojulis interrupta and Thalasoma lunare are more abundant in natural reefs than in artificial coastlines. Diodon holocanthus, Sphyraena flavicauda and Abudefduf sordidus are in reversed situation. The possible reasons for the change of fish assemblages and the decrease of species diversity are the lack of sessile and encrusting organisms and shelters for small reef fishes causing the habitat and food resources in the artificial coastlines much less than those of the natural coastlines. To maintain the diversity and stability of coastline ecology, it is very important to stop further coastal urbanization or breakwater installation along the coastlines.
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