Influence of Reservoir Impoundment on the Cave Habitat of the Unique Cavefish Species Sinocyclocheilus Tileihornes

China possesses the highest species richness of cavefish over the world. Nearly one-third of the recorded cavefish species have been found in China. Among them, the species belonging to Sinocyclocheilus have only been found in China, and mainly distributed in the Yunnan-Guizhou Plateau, where develop a large number of caves and underground rivers. Habitats of most cavefishes are limited in enclosed caves or underground rivers, which have very stable environmental conditions, especially water quality and water temperature. A slight change may cause devastating effect. Changes in habitat conditions of the Sinocyclocheilus have been caused by human activities, like mountain quarrying, groundwater utilization, water pollution, and dam construction. In this study, we carried out more than one year’s continuous habitat measurement of the Sinocyclocheilus Tileihornes in Yunnan Province, attempting to offer an example of how human activities influence the survival of cavefish. Based on the field investigation and the breeding experiments of the species Sinocyclocheilus Rhinoceros, Sinocyclocheilus qujingensis, Sinocyclocheilus graham, and Sinocyclocheilus xichouensis, it was found that the suitable water temperature for spawning and living of Sinocyclocheilus Tileihornes was between 16.5 °C and 18.5 °C. Either a higher or a lower temperature would affect the normal metabolic activity of the species and thus threaten its survival. At the present, a dam is under construction at the downstream of the underground river, in which Sinocyclocheilus Tileihornes inhabits. After the reservoir impoundment, most of the underground river will be submerged and filled up with surface river water, which will for sure change the constant temperature condition of the underground river system. Numerical simulation applying fish habitat model suggested that the temperature cavefish habitat will varied by 10 °C, with the lowest temperature in winter being around 10 °C, while the highest temperature in summer up to 20 °C. The cavefish will have to swim away from the underground river outlet and the river sections with skylights, which are the major food supply areas. Moreover, the area of suitable habitat that has favorable water temperature, water depth, and flow velocity will reduce significantly. It is crucial to provide potential conservation strategies for the cavefish considering biodiversity protection and special research values of the species.

Keywords: cavefish conservation, dam construction, reservoir impoundment, habitat model, water temperature