An estimate of genetic and ecological influence on the coldwater-adapted freshwater fishes by artificially induced environmental alterlations in river systems

为评价人工环境改变对北海道南部部分河流生态系统冷水适应鱼类的遗传和生态影响，对人工环境改变河段和自然曲流河段的目标鱼类生活史特征和遗传种群结构进行了比较研究，得到了流动结果：(1)北海道南部部分河流种群规模、种群数量、种群数量、种群数量、种群数量、种群数量、种群数量、种群数量、种群数量、种群数量等。比较了混凝土堤岸人工伸直河段和自然曲流河段的雷氏夜蛾幼虫密度和生境偏好。因此，幼虫的种群规模和密度要大于受限河段，这主要是由于受限河段的沙泥底分布较多，而沙泥底是幼虫的首选栖息地。从生境偏好的角度来看，雷氏夜蛾幼虫更喜欢栖息在由细颗粒和较深基质组成的砂泥底。(2)对位于Tomakomai市附近的西塔浦河（西塔浦河于1957年在河中游修建了大堰）下游无产卵种群与上游常住种群的三刺棘鱼（Gasterosteus aculeatus）遗传种群结构和生活史特征进行了比较。结果表明，两个群体的等位酶基因频率存在显著差异。在繁殖季节，上游河居种群的体型比下游河居种群小，年龄构成比下游河居种群高。这些结果表明，在堰建后约40年的时间里，内陆种群已经从祖先的溯河种群在遗传和生态上进行了进化。(3)利用微卫星DNA基因标记，比较了北海道南部3条河流中分别分布的白斑鲑（Salvelinus leucomaenis）下游溯河种群与上游居河种群间的遗传变异和种群间的遗传分化。因此，河栖型的平均杂合度比河栖型低70%左右。此外，溯河种群与河栖种群之间的FST值（0.02 ~ 0.225）清楚地表明后者与前者在遗传上存在差异。统计分析表明，两种类型的遗传分化程度与河居型与溯河型分离的年份呈正相关，与各自河流的总流量负相关。(4)在现有研究的基础上，认为河道平直度、堰坝建设等人为环境改变会对适应冷水的鱼类的生物多样性产生负面影响。少

In oder to estimate the genetic and ecological influence on coldwater-adapted fishes by artificially induced environmental alterlations in river systems, the comparative studies on life-history characteristics and genetic population structure were carried out for some targetting fishes inhabiting the artificially-altered reaches and naturally-meandering reaches, and flowing results were obtained :(1) In the some rivers of southern Hokkaido Island, the population sizes, densities and habitat preferences of Lethenteron reissneri larvae were compared between those in artificially-straighten reaches by both the concrete-blocked banks and in naturally-meandering reaches. In consequence, the population sizes and densities of larvae were larger than those in the straitened reaches, mainly because more number of sandy-mud bottoms which were preferencially inhabited by the larvae were scattered in the former reaches. These results obtained from field survey and the other laboratory experiments … More of habitat preference suggest that Lethenteron reissneri larvae prefer to inhabit the sandy-mud bottoms composed of fine particle and deeper substrate.(2) In the Nishitappu River, which is located near Tomakomai City and has a big weir constructed in 1957 at the middle course of the river, the genetic population structure and life-history characteristics were compared between the downstream anadromous population and the upstream river-resident population of threespined stickleback, Gasterosteus aculeatus. As the result, a significant difference was found in the allozymic gene frequency between the two populations. The upstream river-resident population showed smaller body size and higher age composition at breeding season than the downstream anadromous population. These results demonstrate that the land-locked population has evolved genetically and ecologically from the ancestral anadromous stock for about 40 years after the construction of weir.(3) In three rivers of southern Hokkaido Island, the genetic variability within populations and genetic divergence among populations were compared using microsatellite DNA gene markers between the downstream anadromous and upstream river-resident populations of white-spotted charr, Salvelinus leucomaenis, which were separately distributed by dams. Consequently, the river-resident forms showed about 70% low mean heterozygosities, compared to those in the anadromous forms. Furthermore, the FST values (0.02-0.225) between the anadromous and river-resident forms clearly demonstrated that the latter forms were genetically divergent from the former forms. Statistic analyses indicate that the extent of genetic divergence between the two forms were positively correlated with the years for which the river-resident forms had been isolated from the anadromous forms, and negatively correlated with the whole waterflows in respecive rivers.(4) On the basis of present study, artificially environmental alterations of river structures such as straightness of river courses and construction of weirs or dams are concluded to influence negatively on the biodiversity in coldwater-adapted fishes. Less