During the course of this project (July 1995 to June 1996), along the Lakulaku River Watershed in the eastern part of Yushan National Park, we had done the water quality survey and had briefly investigated the composition as well as the distribution of the aquatic fauna there. Areas where Lakulaku River flows through display a gorge topography with continuous carved patterns. Along each side of the stream are luxuriant primitive forests. The stream water is crystal clear most of the time. However, because of the presence of many large crumble terrain at the upper middle reaches, the water of Lakulaku main stream turns into turbid gray, every year, during the heavy flow period (May to November). The stream water is slightly alkaline (pH7.9~8.8). The water temperature is low upstream and turns slightly higher proceeding middle down stream. The water temperature is not significantly different. These facts fully demonstrate the unique feature of a primitive mountain stream. During the research period, we had recorded 11 species of fishes, 2 families 2 species of freshwater prawns, 2 families 2 species of freshwater crabs, and 8 orders 39 families of aquatic insects. Lastly, during the research periods we had recorded 3 families 6 species of amphibians, 8 families 12 species of mammals and 7 families 13 species of stream birds all along the streamside. These all indicate that fauna here is fantastic.