Studies on relations among ecosystem components for lake ecosystem management

我们研究了湖泊红鲑鱼和池塘胡瓜鱼的种群动态，以及十和田湖底栖动物的区系和分布。湖相红鲑的种群动态表现为密度依赖的争夺型。估计的参数表明，鲑鱼幼鱼的生存突然减少时，释放的鱼增加超过200万人。池塘胡瓜鱼并没有表现出密度依赖的死亡率在其产卵招聘关系。多元逐步回归分析结果表明，大马哈鱼丰度与长刺水蚤丰度呈负相关，而塘胡瓜鱼丰度与长刺水蚤丰度呈正相关。longispina和桡足类幼虫。这些结果表明，鲑鱼将与池塘胡瓜鱼竞争食物。结果表明，十和田湖红鲑的种群动态受其种群密度和塘胡瓜鱼丰度的影响，共发现底栖动物53个类群，根据底栖动物区系将湖盆划分为4个区系。1)20 m以下的沿岸的带生物多样性较高; 2）20- 60 m之间的亚沿岸的带寡毛类和摇蚊类22个类群; 3）深海带（不包括Naka-ko最深处）仅4个类群; 4）Naka-ko深海带大型无脊椎动物9个类群。沿岸的带的底部沿从海岸到亚沿岸的带的横断面由卵石、砂和泥组成。卵石层和沙地上的大型无脊椎动物群落生物多样性较高，主要由浮游动物组成，而泥地上的大型无脊椎动物群落生物多样性较低，主要由寡毛类和摇蚊科组成。大型无脊椎动物的生物量在12- 15 m深度最高，但在冬季高峰向较浅的位置移动。这一现象与鱼类在沿岸的分布相结合，说明鱼类的捕食作用控制了大型无脊椎动物群落的分布。

We examined the population dynamics of lacustrine sockeye salmon and pond smelt, and fauna and distribution of benthos in LakeTowada. The lacustrine sockeye salmon showed the scramble type of density-dependence as the population dynamics. Estimated parameters indicated that the survival of salmon juveniles suddenly decrease when released fish increase more than 2 million individuals. Pond smelt did not show density-dependent mortality in their spawner-recruitment relations. Results of stepwise multiple regression analysis showed that the salmon abundance was negatively correlated with Daphnia longispina abundance, and that pond smelt abundance positively correlated with abundance of D. longispina and copepod larvae. These results suggest that salmon would be in competition with pond smelt for the food. We conclude that the population dynamics of lacustrine sockeye salmon is affected by their population density and abundance of pond smelt in the Lake Towada.Fifty-three taxa of benthos were found. The lake basin was divided into 4 parts according to the benthos fauna. 1) littoral zone below 20m depth with a high biodiversity, 2) sublittoral zone between 20-60m depth with 22 taxa of Oligochaeta and chironomids, 3) profundal zone excluding the deepest part Naka-ko with only 4 taxa and 4) Naka-ko profundal zone with 9 taxa of macroinvertebrates. The bottom of the littoral zone changed from cobbles, sand and mud along a transect line from shore to sublittoral zone. The macroinvertebrates communities only in cobbles and sand showed a high biodiversity, mainly composed of lotic species, but those on mud showed a low biodiversity composed of mostly Oligochaeta and Chironomidae. The biomass of macroinvertebrates was highest at 12-15m depth almost, but the peak shifted to the shallower sites during the winter. This phenomenon and the fish distribution in the littoral zone might suggest that the fish predation controls the distribution of the macroinvertebrates community.