| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 102 === Flying &;#64257;shes (Exocoetidae) distribute worldwide in tropical and sub-tropical waters. In the pelagic food web, flying fish serve as a low trophic-level consumer feeding mainly on zooplankton. The eggs of Hirundichthys oxycephalus are harvested off northeastern Taiwan between April and July and adult fish are the major targeted species off the southeastern coast of Taiwan between March and June. In this study, we analyzed the otolith stable oxygen and carbon isotopic composition of the flying fish (Hirundichthys oxycephalus) collected from the coastal waters of Keelung, Hualien, Green Island, and Goto Island, Japan to reconstruct their migratory patterns. We also analyzed the muscle stable carbon and nitrogen isotope composition of the 9 flying fish species and 15 large fish from the waters off eastern Taiwan in order to understand the food web structure. Otolith stable oxygen isotopic composition shows that H. oxycephalus collected from Goto Island all migrated between Japan and Taiwan; H. oxycephalus collected from Keelung, Hualien and Green Island show different migratory life histories, one migrated between Japan and Taiwan, the others were local residence or stay in specific temperature waters. These results suggest diversified migratory patterns of H. oxycephalus in the waters off eastern Taiwan. Stable carbon and nitrogen isotopic composition shows that Cheilopogon cyanopterus has the highest δ15N value and Cheilopogon unicolor has the lowest δ15N value in the 9 flying fish species. There are two trophic levels differences between large predator fish and flying fish in the waters of eastern Taiwan. Muscle δ13C values suggested that flying fish is one of the main prey fed by the Istiophoridae, Xiphias gladius, Coryphaena hippurus and Prionace glauca.
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