The Research of Natural Resources of the Three Northern Islets

Project Duration	2008-01-15 ~ 2009-03-09
Research Title	The Research of Natural Resources of the Three Northern Islets
Contracted Organization	Coral Reef Society of the Republic of China
Principal Investigator	Dai Chang-Feng
Co-Principal Investigators	Chan Jung-Kuei, Wang Chen-Che, Hsu Yu-Feng, Ho Kung-Suan, Wang Shih-Wei, Chang Jui-Sheng, Chen Chih-Hsin, Huang Hsing-Tso
Project Personnel	Chen Jian-Xun, Ho Min-Chieh, Cheng An-Yi, Hung Sheng-Wen, Hsiao Yi-Chen, Liu Yu-Hsing, Chen Ching-Yi, Ho Cheng-Tse, Hsia Kuo-Ching, Tsai Ming-Hsien, Li Kun-Hsuan, Hung Ho-Tien, Liang Ti
Keywords	Northern Three Islets, geomorphology and geology, ecological resources
Abstract	The objective of this project was to establish baseline natural resource data for the Northern Three Islets—Pengjia Islet, Mianhua Islet, and Huaping Islet—and Keelung Islet through literature review and field surveys. Survey components included geology and geomorphology, terrestrial ecological resources, marine ecological resources, and fishery resources. Geologically, these islands were formed by volcanic activity from the Late Pliocene to the Pleistocene. They exhibit well-preserved volcanic landforms and diverse coastal erosion features such as craters, volcanic cones, sea cliffs, wave-cut platforms, sea caves, sea stacks, potholes, and honeycomb weathering. Due to their high tourism and educational value, it is recommended that they be designated as a national-level “Volcanic Geopark.” Terrestrial vegetation surveys recorded 195 vascular plant species in 73 families, including three rare species. Vegetation types were categorized into flat-summit vegetation, sea cliff vegetation, and coastal gravel vegetation. A distinctive Artemisia-dominated shrubland was discovered on Mianhua Islet, representing a previously undocumented vegetation type. Terrestrial fauna surveys documented 33 vertebrate species (21 families) and 41 invertebrate species (24 families). The endemic Taiwan grass lizard was confirmed on Keelung Islet, with evidence of a stable resident population. Rare seabirds, including the Black-naped Tern and Brown Booby, were recorded on Mianhua Islet, suggesting potential breeding habitats. Marine surveys covered 13 dive stations around the four islands. Scleractinian coral coverage ranged from 1.2% to 47.5%, with the highest values at western Mianhua and southwestern Pengjia stations. Overall, coral communities were marginal and non-reef-building, likely influenced by low winter temperatures, strong currents, seasonal monsoons, macroalgal competition, and bioerosion by sea urchins. A total of 112 scleractinian coral species and 21 octocoral species were recorded. Coral assemblages clustered into four groups corresponding largely to individual islands. Benthic invertebrates were dominated by sponges, cnidarians, bivalves, and echinoderms. The sea urchin Echinostrephus aciculatus and small sea cucumbers (Plesiocolochirus sp.) were common, while species abundance differed notably at Keelung Islet. Fish surveys recorded 178 species in 35 families. Labridae was the most species-rich family, followed by Pomacentridae, Acanthuridae, and Chaetodontidae. Cluster analysis showed higher similarity among the Northern Three Islets compared to Keelung Islet, which is more influenced by sedimentation and anthropogenic activities from mainland Taiwan. Macroalgal surveys recorded rich assemblages, including eight species newly recorded for Taiwan. Species composition and coverage varied among islands, with Mianhua and Pengjia exhibiting particularly diverse macroalgal communities. Fishery resource analysis indicated that northern Taiwan waters contribute significantly to national coastal fisheries production. Key fisheries include purse seine (mackerel and scad), trawl, and torchlight fisheries. The Northern Three Islets serve as spawning grounds for economically important species such as squid, mackerel, and flying fish. Therefore, it is recommended that surrounding waters be designated as no-fishing zones to ensure sustainable marine resource utilization.