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

为了重新评价日本的人工繁殖计划，利用鱼鳞档案资料进行了遗传和生态分析。首先确定了大马哈鱼线粒体基因的完整序列。为了在DNA序列上找到蛋白质编码区域的多态性位点，对来自遥远种群的样本进行了比较。测定了线粒体基因ND2区约1000个dna序列。在该区域约200 bp的长度上发现了3个多态性位点。微卫星DNA有6个位点，其中Oke3位点长度变异较大。遗传多样性以岩手居群最高，茨城居群次之，阿拉斯加居群最低。比较不同保存时间鱼鳞中提取DNA的数量和PCR扩增量。对于2年的保存，我们产生了足够数量的优质DNA。从超过10年至30年的样品中提取了降解的DNA，但提取的DNA数量与保存2年的样品相当。1980年代回归岩手县的大马哈鱼体积减小的原因可以解释为回归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，在最近的低回报率期间，回报率的规模恢复到与1980年代初相当。回归率与近岸水温等环境因子的相关分析并不一定显示出显著的关系。为了验证用鱼鳞测定年龄的方法，我们进行了耳石观察。有些耳石的内部是黑色的，这干扰了第一年戒指的清晰视野。我们没有得到任何证据来否定尺度年龄测定的准确性。我们用鱼鳞测量了碳、氮和硫的同位素比率。除硫外，各同位素值有各自的年波动规律。

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.