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Density-Dependent Effect of Chum Salmon, Oncorhynchus Keta, on Growth and Reproduction

鲑鱼 Oncorhynchus Keta 对生长和繁殖的密度依赖性影响

基本信息

批准号：
01560213
负责人：
IDA Hitoshi
金额：
$ 0.83万
依托单位：
Kitasato University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

Since the 1970's the number of chum salmon returned to Japan increased exponentially due to artificial propagation. In recent years, coastal catch of Japanese chum salmon depends by one fourth on Iwate chum salmon and by two third on Hokkaido chum salmon. Incremental ratio of the number of chum salmon returned to Iwata prefecture was higher than other areas in Japan.The aim of this study is to examine the effect of such enhancement of chum salmon stock on biological characteristics of this stock itself.We investigated age and size at maturity of three chum salmon populations in southern Iwate prefecture since 1975. Size decrease was observed since the early 1980's. Also mean age at maturity tended to become higher and condition factor reduced simultaneously.To estimate the growth during ocean resident years, we measured length of scale radii and number of circuli at each ocean resident year. Age 4 fish were subsampled for scale measurement. Though annual variation of length of scale radii and unmber of circuli were observed for each ocean resident year, stunted growth at first ocean year was obvious in recent ten years.Negative correlations were detected between mean fork length and number of adults returned to Iwata prefecture, and between first ocean growth and number of Iwate juvenile chum salmon released. Positive correlation existed between mean age of return and number of adults returned to Iwata prefecture. From these results existence of density dependent growth of first ocean growth was suggested.

自20世纪70年代以来，由于人工繁殖，回到日本的鲑鱼数量呈指数级增长。近年来，日本大马哈鱼的沿海捕捞量有四分之一依赖岩手大马哈鱼，三分之二依赖北海道大马哈鱼。岩田县大马哈鱼回笼数量的增量比例高于日本其他地区。本研究的目的是检验这种增强鲑鱼种群对该种群本身生物学特性的影响。自1975年以来，我们调查了岩手县南部三个鲑鱼种群的年龄和成熟时的大小。自20世纪80年代初以来，观察到尺寸减小。平均成熟年龄有升高的趋势，同时条件因子也有降低的趋势。为了估计海洋常驻年的增长，我们测量了每个海洋常驻年的尺度半径长度和环流数。对4岁的鱼进行取样以测量鳞片。虽然各海洋常驻年的尺度半径长度和环数都有年际变化，但近十年来在第一个海洋年出现了明显的生长迟缓现象。平均叉长与返回岩田县的成年鲑鱼数量呈负相关，第一次海洋生长与释放的岩手鲑鱼幼鱼数量呈负相关。平均返乡年龄与成人返乡人数呈正相关。这些结果表明，第一海洋生长存在密度依赖性生长。