Studies on early life history of Anguilla japonica in 1986 survey cruise by R.V. hakuho-maru - IV. Age and birth date of Anguilla japonica leptocephali collected in Western North Pacific in September 1986.
Studies on early life history of Anguilla japonica in 1986 survey cruise by R.V. hakuho-maru - IV. Age and birth date of Anguilla japonica leptocephali collected in Western North Pacific in September 1986.
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1986年R.V. 考察航行对日本鳗鲡早期生活史的研究
DOI：
10.2331/suisan.55.1023
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发表时间：
1989
影响因子：
0.4
通讯作者：
T. Kajihara
中科院分区：
文献类型：
--
作者：
K. Tsukamoto;A. Umezawa;O. Tabeta;N. Mochioka;T. Kajihara
为了确定日本鳗鲡（Anguilla japonica）的产卵季节，本文利用1986年9月在北太平洋西部采集的14只日本鳗鲡耳石的日生长量，估计了日本鳗鲡的年龄和出生日期。头状体的矢状体（40.5 ~ 47.0mm）为半透明的、侧向压缩的椭圆形结构，直径约155μm，中心有一个暗不透明的核心（长轴6μm）。从耳石中心到耳石边缘，在耳石周围观察到明显的同心圆生长增量（环状）。约80%的标本在岩心附近有明显的直径约11μm的暗环（重不连续区），这可能是孵化时形成的“孵化检查”。尾头象的年龄基本一致，为72±3天（平均±SD）。它们的出生日期在1986年6月28日至7月18日之间，平均为7月13日，表明它们在夏季产卵。
In order to determine the spawning season of the Japanese eel Anguilla japonica, age and birth date of the leptocephali were estimated with the daily growth increment in otoliths of 14 specimens collected in Western North Pacific in September 1986.The sagittae of the leptocephali (40.5-47.0mm in TL) were translucent, laterally compressed oval structures of about 155μm diameter with a dark opaque core (6μm in long axis) in the center. Distinct concentric growth increments (ring) were observed around the core from the center till the edge of otolith. About 80% specimens examined had a distinct dark ring (heavy discontinuous zone) with about 11μm diameter near the core, which seemed to be a “hatch check” formed at hatching.The age of leptocephali was nearly uniform, 72±3 days (mean±SD). Their birth date ranged from June 28 to July 18, 1986 and the mean was July 13, suggesting that this species spawns in summer.