Migratory history of the Japanese eeI Anguilla japonica, as revealed by otolith microchemistry and stable isotope markers

对采自大村湾(熊本县54条黄鳗)、久马河口(长崎市48条黄鳗)和东海中国(7条银鳗)的日本鳗鱼耳石中的锶(锶)和钙(Ca)进行了X射线能谱分析。耳石中的锶/钙比值随个体发育和生境盐度的变化而变化。淡水线外的锶/钙比值的模式变化反映了三种类型的迁徙历史：(A)河鳗，(B)河口鳗鱼，(C)河口鳗鱼，河流生命周期短。根据耳石的锶/钙比值，A型出现的频率分别为：大村湾14%、龟马河口15%、东中国海14%；(B)、大村湾74%、龟马河口62%、东中国海43%、(C)、大村湾12%、龟马河口23%、东中国海43%。各类型间生长差异不显著。

Environmental history of the Japanese eel Anguilla japonica collected from Omura Bay (54 Yellow eels, Kumamoto Pref.), Kuma River estuary (48 Yellow eels, Nagasaki Oref.), and East China Sea (7 Silver eels) were studied by examining strontium (Sr) and calcium (Ca) in their otoliths with wavelength dispersive X-ray spectrometry on an electron microprobe. The Sr/Ca ratios in the otoliths changes with both ontogenetic development and salinity of the habitat. The rarios significantly different between brackish and fresh water.The pattern change of the Sr/Ca ratios outside the freshwater mark indicated three types of migratory history : (A) river eels, (B) estuarines eels and (C) estuarine eeis with short period river life. According to the otolith Sr/Ca ratios, the occurrence of type A was 14% for Omura Bay, 15% for Kuma river estuary, and 14% for East China Sea and that of (B), 74% for Omura Bay, 62% for Kuma river estuary, 43% for East China Sea and that of (C), 12% for Omura Bay, 23% for Kuma river estuary, 43% for East China Sea. There was no difference in growth between each types.