Effects of the First Phase of Jinsha River Hydropower Project on Fish Recruitment:Early Life History Stages of Coreius guichenoti in the Upper Yangtze River

GAO Shao-bo;TANG Hui-yuan;CHEN Sheng;YANG Zhi;DONG Fang-yong;Key Laboratory of Ecological Impacts of Hydraulic-Projects and Restoration of Aquatic Ecosystem of Ministry of Water Resources,Institute of Hydroecology,Ministry of Water Resources and Chinese Academy of Sciences;

the first phase of Jinsha River project;;the National Nature Reserve of Rare and Endemic Fish in the upper Yangtze River;;Coreius guichenoti;;fish resources of early life history stages;;recruitment

Coreius guichenoti is an important commercial fish endemic to the upper Yangtze River and one of the primary species with priority for protection in the National Nature Reserve of Rare and Endemic Fish in the upper Yangtze River. Under natural conditions,spawning and reproduction of Coreius guichenoti are accomplished in the middle and lower reaches of the Jinsha River and meets necessary fish recruitment of early stage Coreius guichenoti for the reserve. The first phase of the Jinsha River Project is comprised of two cascaded power stations( Xiangjiaba and Xiluodu) located in the upper reaches of the reserve. The cofferdam closure of Xiangjiaba and Xiluodu hydropower stations( December,2008 and November,2007) and subsequent filling( October,2012 and May,2013)have significantly affected the life history of Coreius guichenoti and fish recruitment of early stage Coreius guichenoti in the reserve. To accurately evaluate the influence of the project,we undertook a five-year investigation on Coreius guichenoti eggs and larvae at two locations in the lower Jinsha River during construction of the first phase of the hydropower project,that will provide a reference point for conserving Coreius guichenoti. The investigations of fish eggs and larvae were made in the Shuifu section of the Jinsha River in 2008( 3 km from Xiangjiaba Dam) and in the Yibing section in 2010- 2013( 28 km from Xiangjiaba Dam). Conical nets with a 0. 39 m2 opening were fixed in the water 10- 20 m away from the bank and perpendicular to the flow. Fish eggs and larvae drifting into the nets were collected during the time intervals 6 ∶ 00- 10 ∶ 00,14 ∶ 00- 18 ∶ 00 and 22 ∶ 00- 2 ∶ 00 and for 15-30 min during each interval. The development stages of fish eggs and larvae were assessed under an anatomical lens. Species identification of larvae was conducted in situ and fish eggs were incubated into larvae for species determination. A total of 6 190 Coreius guichenoti eggs and larvae were collected during the five years,including 74 eggs and 6 116 larvae. However,no eggs or larvae were captured in 2013 after the impoundment of the Xiangjiaba Reservoir. The density of Coreius guichenoti eggs and larvae peaked from June 12 to July 2 in 2008,June 22 to July10 in 2010,June 23 to July 4 in 2011 and from June 24 to July 13 in 2012,with highest daily yields of 3. 79 ×107ind,3. 47 × 107 ind,9. 58 × 107 ind and 1. 22 × 107 ind,respectively. Overall,the spawning of Coreius guichenoti peaked from late June to early July,lasting 2- 3 weeks,corresponding to a continuously rising flow and flooding in the lower Jinsha River. In 2008,before the cofferdam closure of the Xiangjiaba Hydropower Station,an estimated 2. 12 × 108 Coreius guichenoti eggs and larvae drifted into the National Nature Reserve of Rare and Endemic Fish in the upper Yangtze River,while during the construction period in 2010- 2012,the recruitments of Coreius guichenoti eggs and larvae in the national reserve were estimated at 1. 65 × 108 ind,1. 61 × 108 ind,0. 82 ×108ind,respectively. The downward trend was followed by no observed recruitment in 2013. We conclude that the cascaded hydropower stations at Xiluodu and Xiangjiaba block flotation of Coreius guichenoti eggs and larvae to the nature reserve and negatively influence early life stages of Coreius guichenoti in the nature reserve.