金沙江一期工程对保护区圆口铜鱼早期资源补充的影响

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

2008、2010-2013年在金沙江下游水富/宜宾断面进行了鱼类早期资源调查,研究金沙江一期工程对长江上游珍稀特有鱼类国家级自然保护区圆口铜鱼早期资源补充的影响。共采获圆口铜鱼卵苗6 190粒（尾）,其中鱼卵74粒、鱼苗6 116尾;2013年向家坝水电站蓄水后在水富/宜宾断面未采集到圆口铜鱼卵、苗。各年圆口铜鱼卵苗江汛期和最大日径流量分别为：2008年6月12日-7月2日、3.79×10^7粒（尾）,2010年6月22日-7月10日、3.47×10^7粒（尾）;2011年6月23日-7月4日、9.58×10^7粒（尾）;2012年6月24日-7月13日、1.22×10^7粒（尾）。圆口铜鱼卵苗江汛与金沙江下游的水文流量持续增长相关,卵苗日径流量高峰值与洪峰过程较一致,最大日径流量基本先于最大水文流量前出现。圆口铜鱼繁殖盛期在6月中旬-7月上旬较短时间内（2～3周）。2008年向家坝水电站截流前长江上游珍稀特有鱼类国家级自然保护区的圆口铜鱼早期资源补充量为2.12亿粒（尾）;2010-2012年导流施工期间早期资源补充量分别为1.65亿、1.61亿、0.82亿粒（尾）,呈下降趋势;2013年无早期资源补充。溪洛渡、向家坝2个梯级大坝一定程度上阻隔了圆口铜鱼卵苗向下游漂流的途径。要合理制定水电梯级调度方案,促进或引起圆口铜鱼自然繁殖过程,并降低圆口铜鱼卵苗在库区的死亡率;加强圆口铜鱼现有栖息地保护,严格控制或禁止在产卵场捕捞亲鱼;开展圆口铜鱼在梯级大坝上下游间群体交流连通性的可能性研究和圆口铜鱼全人工繁殖技术研究。

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 m^2 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 ×10^7 ind,3. 47 ×10^7 ind,9. 58 ×10^7 ind and 1. 22 ×10^7 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 × 10^8 ind,1. 61 × 10^8 ind,0. 82 ×10^8 ind,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.