Fig. 1

a Sampling sites. The sampling map was created using ArcGIS v10.1 (ESRI, CA, USA), and processed using Adobe Illustrator CS5 (Adobe System Inc., San Francisco, CA, USA). Data used in the map was downloaded from National Science & Technology Infrastructure of China (http://lake.geodata.cn) and http://www.statsilk.com/maps. Fish photo in (a) belongs to Dr. Kai Zhao. b Annual water temperature (y-axis on the right) and hours of light time (y-axis on left). The water temperature was measured about 0–0.7 m beneath the water surface of the Lake Qinghai. No data on water temperature was available in Jan and Feb due to the icing in the winter of the Lake Qinghai. The light hours reach the peak in May, and keep as the long day during from May to Aug. The decrease in light hours from Jun to Aug is primarily due to the rainy season in the summer. The environmental and ecological data collected from 1988 to 2004 [20]