Reevaluation of chum salmon artificial propagation in Japan using genetic retrospective analysis

为了重新评估日本的人工繁殖计划，利用鱼鳞档案进行了遗传和生态分析。首先测定了大麻哈鱼线粒体基因的全序列。为了寻找DNA序列上蛋白质编码区的多态性位点，比较了来自遥远种群的样品。测定了线粒体基因ND2区约1000 bp的序列。在200 bp左右的长度范围内发现了3个多态性位点。微卫星DNA共检测到6个位点，其中Oke3位点的长度变异较大。岩手居群的遗传多样性最高，其次是茨木居群，阿拉斯加居群最低。比较不同保存时间鱼鳞DNA提取量和PCR扩增结果。保存2年，我们产生了足够数量的DNA质量良好。从10年以上至30年降解的样品中提取DNA量与保存2年的样品相当的样品。在20世纪80年代返回岩手县的鲑鱼的大小减少被解释为在第一次和返回前一年的生长发育迟缓，这是密度依赖效应的结果。另一方面，在最近的低回报率时期，回报规模恢复到与20世纪80年代初相当的水平。回归率与海岸温度等环境因子的相关性分析表明，回归率与环境因子的相关性不显著。为了验证鱼鳞年龄测定方法，我们尝试了耳石观察。有些耳石内部颜色较深，影响了年轮的清晰度。我们没有得到任何证据来否定鳞片年龄测定的准确性。我们测量了碳，氮和硫同位素比值使用chum尺度。除硫外，各同位素值均有其年变化规律。

To reevaluate artificial propagation program in Japan genetic and ecological analysis were conducted utilizing fish scale archives. Firstly a complete sequence of mitochondrial gene was determined for chum salmon. To find polymorphic sites in protein coding regions on DNA sequences samples from remotely distanced populations are compared. Sequences of about 1000 by in ND2 region on mitochondrial gene were determined. Three polymorphic sites were found in about 200 bp length with that region. As for microsatellite DNA 6 loci were investigated, and high length variation was observed on Oke3 locus. Genetic diversity was highest in Iwate population, followed by Ibaraki population and lowest in Alaska population. The amount and PCR amplification of extracted DNA from archived fish scales were compared among the durations of time for preservation. For 2 years preservation we yield enough amount of DNA with good qualities. From samples older than 10 up to 30 years degraded but comparable amount of DNA to 2 years preservation samples was extracted. Size decrease of chum salmon returned to Iwate prefecture in 1980s was explained by stunted growth at first and a year before return, which is a result of density dependent effect. On the other hand during recent low return rate period, size at return was recovered comparable to that in early 1980s. The correlation analysis between return rate and environmental factors such as water temperature near shore did not necessarily show significant relationships. To validate the age determination method using fish scales we tried otolith observation. Some otoliths have dark inner part, which disturbed the clear view of first year rings. We did not get any proof to deny the accuracy of scale age determination. We measured carbon, nitrogen and sulfur isotope ratios using chum scales. Except for sulfur each isotope value had own pattern of annual fluctuation.