Evidence for migration of metamorphosing larvae of Anguilla japonica in the Kuroshio

Two sampling surveys of the R/V Tansei Maru were conducted in the Kuroshio region south of Kyushu Island of Japan and to the south in the western North Pacific, to study the distribution patterns of the larval stages of the Japanese eel Anguilla japonica as they approach their recruitment areas in East Asia. Nine fully-grown premetamorphic leptocephali (49.5-58.3mm TL) were collected during November 1996 to the east of Taiwan. During November and December 2000, nine early stage glass eels (51.3-57.0mm TL, pigmentation stage II-IV) that were still in the late metamorphosis stages were collected in the Kuroshio. These findings suggest that metamorphosing Japanese eel leptocephali that recruit to the northern part of their species range migrate in the Kuroshio. They may detrain from the Kuroshio at the pigmentation stage IV-VA and begin their coastal migration

土佐湾及び四国沖黒潮流域で採集されたウナギ目魚類レプトケファルス幼生の分布

土佐湾及び四隅沖黒潮流域で、1990年1月にウナギ目魚類レプトケファルス幼生の採集を行った。採集は丸稚ネット(口径1.3m、網口面積1.33㎡、目合O.33mm)による傾斜曳あるいはステップ曳と高速稚魚ネット(網口面積2.03㎡、目合2.0mm)による表層曳で行われた。計41尾のレプトケファルス幼生が黒潮流域で採れた。その内訳はギンアナゴGnathophis nystromi nystromi(JORDAN et SNYDER)(33尾)、ニラミアナゴ属sp. 5 Ariesoma sp. 5(1尾)、ニラミアナゴ属sp. 7 Ariosoma sp. 7(2尾)、クロアナゴConger japonicus BLEEKER(1尾)、クロアナゴ亜科sp. 1 Congrinae sp. 1(2尾)、メクラアナゴDysomma anguillare BARNARD(2尾)であった。全個体の82.9%(34尾)が黒潮南外側域に分布していた。またギンアナゴは全個体が表層曳で、それ以外は全でステップ曳(ワイヤー長;500, 400, 300, 200, 100m)で採集された。A total of 41 leptocephali was collected in the Kuroshio waters off Shikoku Island. They included 33 Gnathophis nystromi nystromi (JORDAN et SNYDER), one Ariosoma sp. 5, two Ariosoma sp. 7, one Conger japonicus BLEEKER, two Congrinae sp. 1, and two Dysomma anguillare BARNARD. Most of leptocephali collected (82.9% of a total catch) were occurred in the southern boundary of the Kuroshio Current. All the Gnathophis leptocephali were collected with the surface horizontal tow of High Speed Larva Net, and the other leptocephali were with step tow of Larva Net

Evidence for migration of metamorphosing larvae of Anguilla japonica in the Kuroshio

Two sampling surveys of the R/V Tansei Maru were conducted in the Kuroshio region south of Kyushu Island of Japan and to the south in the western North Pacific, to study the distribution patterns of the larval stages of the Japanese eel Anguilla japonica as they approach their recruitment areas in East Asia. Nine fully-grown premetamorphic leptocephali (49.5-58.3mm TL) were collected during November 1996 to the east of Taiwan. During November and December 2000, nine early stage glass eels (51.3-57.0mm TL, pigmentation stage II-IV) that were still in the late metamorphosis stages were collected in the Kuroshio. These findings suggest that metamorphosing Japanese eel leptocephali that recruit to the northern part of their species range migrate in the Kuroshio. They may detrain from the Kuroshio at the pigmentation stage IV-VA and begin their coastal migration