11:30 〜 11:45
[HTT16-10] 魚骨鉛同位体比分析による魚類の生育場・回遊履歴の解析
キーワード：鉛同位体、魚骨、産地判別、回遊履歴
Lead (Pb) isotopes will be a useful tracer that enable to discern geographic origin of marine fishes because the average residence time of Pb in the ocean is short (about 10 to 100 years) and Pb isotopes have characteristic values in each oceanic region reflecting different anthropogenic Pb sources. Pb is highly accumulated in fish bones up to several ppm, allowing us to measure Pb isotopes with a small amount of bone samples. Therefore, fine bone Pb isotope ratios have a potential as a new method to trace migration patterns and/or to determine geographic origin of even small and juvenile fishes.
In this study, we measured Pb isotopes of Mackerels and Horse mackerels inhabited in the Japan Sea, the East China Sea, the western North Pacific, and the North Atlantic (totally 163 samples). Bones were digested by ultrapure HNO3, and Pb was separated from bulk solution using either Sr resin (Eichrom) or anion resion. Then, Pb isotopes were measured by a MC-ICP-MS (NEPTUNE, Thermo Scientific) at RIHN.
Atlantic mackerels habited (n = 23) in the North Atlantic and Blue mackerels (n = 50) habited near Japan represented distinctly different 208Pb/206Pb ratios. Likewise, Atlantic horse mackerels, Japanese scads, and Japanese jack mackerels in the Atlantic and near Japan also showed different 208Pb/206Pb ratios. These fish bone Pb isotopes of Mackerels and Horse mackerels obtained from the Northwest Pacific and the North Atlantic exhibited almost identical Pb isotopic compositions of the surface seawaters where fishes grew. This consistency between fish bone and seawater Pb isotopes suggests that fish bone Pb isotopes faithfully record seawater Pb isotopes. Cluster analysis based on fish bone Pb isotopes shows that geographic origins of Atlantic and Northwest Pacific fishes can be identified.
We also found a large scater of Pb isotope in Japanese jack mackerels (n = 19) caught in Kurobe (Toyama Bay), which can be interpreted as reflecting some fishes had migrated between the East China Sea and Japan Sea and some fishes had not migrated seasonally down to the Each China Sea. Similar scattering of Pb isotopes was also found in Blue mackerels habited in the Pacific Ocean near Japan. These scatters were strongly related to the ages of fishes; elder fishes tended to show lower 208Pb/206Pb ratios, which might reflect a migration pattern biased toward the upstream Kuroshio Current. In summary, we concluded that fine bone Pb isotope ratios can trace a north-south migration pattern and identify a geographic origin of marine fishes at least Mackerel and Horse mackerel of North Atlantic and Northwest Pacific, respectively.
In this study, we measured Pb isotopes of Mackerels and Horse mackerels inhabited in the Japan Sea, the East China Sea, the western North Pacific, and the North Atlantic (totally 163 samples). Bones were digested by ultrapure HNO3, and Pb was separated from bulk solution using either Sr resin (Eichrom) or anion resion. Then, Pb isotopes were measured by a MC-ICP-MS (NEPTUNE, Thermo Scientific) at RIHN.
Atlantic mackerels habited (n = 23) in the North Atlantic and Blue mackerels (n = 50) habited near Japan represented distinctly different 208Pb/206Pb ratios. Likewise, Atlantic horse mackerels, Japanese scads, and Japanese jack mackerels in the Atlantic and near Japan also showed different 208Pb/206Pb ratios. These fish bone Pb isotopes of Mackerels and Horse mackerels obtained from the Northwest Pacific and the North Atlantic exhibited almost identical Pb isotopic compositions of the surface seawaters where fishes grew. This consistency between fish bone and seawater Pb isotopes suggests that fish bone Pb isotopes faithfully record seawater Pb isotopes. Cluster analysis based on fish bone Pb isotopes shows that geographic origins of Atlantic and Northwest Pacific fishes can be identified.
We also found a large scater of Pb isotope in Japanese jack mackerels (n = 19) caught in Kurobe (Toyama Bay), which can be interpreted as reflecting some fishes had migrated between the East China Sea and Japan Sea and some fishes had not migrated seasonally down to the Each China Sea. Similar scattering of Pb isotopes was also found in Blue mackerels habited in the Pacific Ocean near Japan. These scatters were strongly related to the ages of fishes; elder fishes tended to show lower 208Pb/206Pb ratios, which might reflect a migration pattern biased toward the upstream Kuroshio Current. In summary, we concluded that fine bone Pb isotope ratios can trace a north-south migration pattern and identify a geographic origin of marine fishes at least Mackerel and Horse mackerel of North Atlantic and Northwest Pacific, respectively.