Stable Isotope Ratios of Carbon and Nitrogen and Mercury Concentrations in 13 Toothed Whale Species Taken from the Western Pacific Ocean off Japan

Stable isotope ratios of carbon (partial derivative(13)C) and nitrogen (partial derivative(15)N) and total mercury (T-Hg) concentrations were measured in red meat samples from 11 odontocete species (toothed whales, dolphins, and porpoises) sold in Japan (n = 96) and in muscle samples from stranded killer whales (n = 6) and melon-headed whales (n = 15), and the analytical data for these species were classified into three regions (northern, central, and southern Japan) depending on the locations in which they were caught or stranded. The partial derivative(15)N in the samples from southern Japan tended to be lower than that in samples from the north, whereas both partial derivative(13)c and T-Hg concentrations in samples from the south tended to higher than those in samples from northern Japan. Negative correlations were found between the partial derivative(13)C and partial derivative(15)N values and between the partial derivative(15)N value and T-Hg concentrations in the combined samples all three regions (gamma= -0.238, n = 117, P < 0.01). The partial derivative(13)C, partial derivative(15)N, and T-Hg concentrations in the samples varied more by habitat than by species. Spatial variations in partial derivative(13)C, partial derivative(15)N, and T-Hg concentrations in the ocean may be the cause of these phenomena.