中文摘要：

怀沙河和怀九河是两条自然汇入北京怀柔水库的河流，被规划为北京市第一个市级水生野生动物保护区。2004年3月～2005年2月，作者对该保护区内野生鱼类资源进行了本底调查。调查区域内野生淡水鱼类共计24种（不计引入种），隶属于6目11科24属，以鲤形目鲤科鱼类为主，多为山区溪流小型鱼类。鱼类物种多样性在空间分布上有所不同，两河下游近水库河段物种多样性最高，这可能与两个不同生态环境交界处的边缘效应有关；其多样性在时间上春夏季高于秋冬季。结合区域内的生境特点，建议加强对核心区的保护力度，重新规划缓冲区和过渡区；在保护自然环境的同时，兼顾当地居民的经济利益，达到人与资源的和谐发展。

英文摘要：

The Huaisha-Huaijiu Rivers flow separately into the Huairou Reservoir, which is an important source of drinking water for the city of Beijing. The rivers plus the reservoir together comprise the first Aquatic Nature Reserve in Beijing. Field studies on the wild fish resources of these rivers were conducted from March 2004 to February 2005, with a resulting count of 24 species of the freshwater fish belonging to 24 genera, 11 families and 6 orders. Most species are eyprinids with small bodies living in the streams. In both rivers, the areas immediately adjacent to the reservoir possess the highest levels of fish species diversity, perhaps due to the edge effects from the different habitats. Fish species diversity is higher in spring and summer than in other two seasons. In addition, the level of fish resources （population level） in Huaijiu River is higher than in Huaisha River. This is mainly attributed to the high population levels at the Xisiduhe site. To ensure productive long-term use the Huaisha and Huaijiu Rivers and the Huairou reservoir, their aquatic resources should be protected while developing the local economy.