Examinando por Autor "Yamamoto, T."

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    Contaminants in tracked seabirds showing regional patterns of marine pollution
    (2013) Ito, A.; Yamashita, R.; Takada, H.; Yamamoto, T.; Shiomi, K.; Zavalaga, C.; Abe T.; Watanabe S.; Yamamoto, M.; Sato K.; Kohno H.; Yoda, K.; Iida T.; Watanuki Y.
    Ocean-scale monitoring of pollution is challenging. Seabirds are useful indicators because they travel over a broad foraging range. Nevertheless, this coarse spatial resolution is not fine enough to discriminate pollution in a finer scale. Previous studies have demonstrated that pollution levels are higher in the Sea of Japan and South and East China Seas than the Northen Pacific Ocean. To test these findings in a wide-ranging animal, we tracked streaked shearwaters (Calonectris leucomelas) from four islands in Japan using global positioning system (GPS) and measured persistent organic pollutants (POPs) in the oil of their preen glands. The POPs did not change during 6 to 21 days when birds from Awashima were foraging only in the Sea of Japan, while it increased when they crossed to the Pacific through the Tsugaru Strait and foraged along the eastern coast of Hokkaido where industrial cities occur. These results indicate that POPs in the oil reflect relatively short-term exposure. Concentrations of POPs displayed greater variation among regions. Total polychlorinated biphenyls were highest in birds foraging in a small area of the semiclosed Seto Inland Sea surrounded by urbanized coast, p,p″- dichlorodiphenyltrichloroethane (DDT) was highest in birds foraging in the East China Sea, and total hexachlorocyclohexanes were highest in birds foraging in the Sea of Japan. All were lowest in birds foraging in the Pacific. This distribution of POPs concentration partly agrees with previous findings based on mussels, fish, and seawater and possibly reflects the mobility and emission sources of each type of POP. These results highlight the importance of information on the foraging area of highly mobile top predators to make them more effective monitors of regional marine pollution. © 2013 American Chemical Society.
  • Miniatura
    ÍtemAcceso Abierto
    Sex-related differences in the foraging movement of streaked shearwaters calonectris leucomelas breeding on Awashima Island in the sea of Japan
    (Ornithological Society of Japan, 2017) Matsumoto, S.; Yamamoto, T.; Yamamoto, M.; Zavalaga, C.B.; Yoda, K.
    Sex-related differences in foraging habitat are common among seabirds. Streaked Shearwaters Calonectris leucomelas breeding on Awashima Island in the Sea of Japan are considered to exhibit gender differences in foraging habitat: only males cross the windy Tsugaru Strait into the Pacific Ocean. Since males are larger, with greater wing loading than females, winds are expected to increase the effect of sexual size dimorphism on their flight performance, which may determine accessibility to foraging habitats. To assess the sex-related differences in foraging movements among years in which environmental and wind conditions differed, we analyzed foraging trips of male (N=243) and female (N=241) Streaked Shearwaters during the chick-rearing period by using GPS loggers in 2011, 2012, and 2013. Both males and females were found to travel through the Tsugaru Strait into the Pacific Ocean, but the frequency was higher for males than for females. Nevertheless, we found that wind velocities had no effect on the probability of transiting the Tsugaru Strait. Greater wing loading requires higher energy demands for flight; therefore, males possibly needed to travel into the Pacific Ocean to feed on the energy-rich Pacific Saury Cololabis saira. In 2012, when the sea surface temperature (SST) in the Sea of Japan was the highest among the three study years, the frequency of foraging in the Pacific Ocean was similar for males and females. Shearwaters are considered to forage in association with predatory fish, the distribution of which is largely influenced by the Tsushima Warm Current migrating partially into the Tsugaru Strait. Hence, both males and females were more likely to travel into the Pacific Ocean when the Sea of Japan SST was high, generating conditional sex-related differences in foraging habitat. © The Ornithological Society of Japan 2017.