Abstract
We investigated the fish fauna at 40 stations in the mainstream and 13 tributraries of the Sagami River system. As the result, 42 species belonging to 15 families collected. They comprised 29 genuine freshwater, 11 diadromous and 2 peripheral freshwater species. Of genuine freshwater species, the number of domestic alien species is more than those of the native. The fish species occurred in high frequency were in order of Phoxinus lagowskii steindachneri, Oncorhynchus masou masou, Tribolodon hakonensis, Cobitis biwae, Rhinogobius sp. OR and Zacco platypus. Larger tributary has high diversity in the number of species, and the number exceeds those of the mainstream. They were in order of the Koayu River, Nagaike River and Tama River.
