长江上游江津段寡鳞飘鱼早期资源研究

Early Resource Investigation of Pseudolaubuca engraulis( Nichols) in the Jiangjin Section of the Upper Yangtze River

寡鳞飘鱼(Pseudolaubuca engraulis)作为许多肉食性鱼类重要的饵料来源,长期以来缺乏对其早期生活史阶段特别是重要产卵场资源量变动、早期发育方面的研究。为探究寡鳞飘鱼早期资源量在金沙江一期工程蓄水前后的变化情况,并了解其早期发育状况,于2011-2015年的每年5月5日至7月10日在长江上游江津断面进行鱼类早期资源调查的同时,对采集到的鱼卵早期发育进行研究。结果表明,2011-2015年,寡鳞飘鱼卵苗总径流量分别为2.964×10~8粒(尾)、2.759×10~8粒(尾)、1.335×10~8粒(尾)、1.758×10~8粒(尾)、3.926×10~8粒(尾);金沙江一期工程蓄水后,江津断面寡鳞飘鱼卵苗总径流量和卵苗日均密度均呈逐年递增趋势,其产卵量占采样期间总产卵量的比例(相对多度)也呈波动上升趋势,已成为蓄水后长江上游宜宾至江津干流江段产卵规模最大的产漂流性卵鱼类;根据鱼类早期发育结果,寡鳞飘鱼的平均卵膜径为(5.44±0.05)mm,平均卵径为(1.61±0.03)mm,初孵仔鱼平均全长(5.07±0.07)mm。

Pseudolaubuca engraulis is an important food source for many carnivorous fish species. However, few studies have been carried out on the early life history of P. engraulis, especially the variability of the resource in spawning grounds and early stages. In this study, we investigated the early life resource of P. engraulis in the Jiangjin section of the upper Yangtze River, from May 5 to July 10, over four years, 2011 - 2015. This time period includes the impoundment of the first phase of the Jinsha River hydroelectric project and eggs were collected for lab observation of the early development of P. engraulis. The objectives of the study were to explore the resource change of P. engraulis associated with construction of the Jinsha River hydroelectric project, evaluate the impact of impoundment and generate a database on the early life stages of P. engraulis. The river section investigated is part of the Rare and Endemic Fish National Nature Reserve on the Upper Yangtze River and the cross-section sampled was located 35 km above the upper reach of Three Georges Reservoir. Twice daily, P. engraulis eggs were collect- ed at three sites along the cross-section （right, left and middle） of the river and at three depths （ surface, middle and bottom）. The sampling time, air temperature, water temperature, transparency, pH and conductivity were re- corded simultaneously. The samples were grouped in situ and transported to the lab for observation of egg character- istics and identification of developmental stage. Some eggs were reared in aerated tap-water for further study of early stage developmental characteristics of P. engraulis. Recruitment of P. engraulis eggs and larvae in the Jiangjin sec- tion from 2011 to 2015 were estimated, respectively, as 2. 964 x 10s ind, 2. 759 x l0s ind, 1. 335 x l0s ind, 1. 758 ~ l0s ind and 3. 926 x lOs ind. After first phase impoundment of the Jinsha River hydroelectric project, the total runoff and average daily density of P. engraulis eggs and larvae increased year by year, and the relative abun- dance of P. engraulis early resources exhibited a fluctuating, but increasing trend in total early fish resources. After impoundment, P. engraulis became the largest source of eggs drifting from Yibin to Jiangjin. Pearson Correlation a- nalysis showed that average daily density of P. engraulis egg was significantly correlated only with water temperature （P 〈 0.05）, indicating that P. engraulis spawning was signaled by water temperature rather than hydrological fac- tors, different from most fish species that spawn drifting eggs. This also explains why the early stage resources and relative abundance of P. engraulis eggs and larvae increased after first phase impoundment. By observing early stage development of P. engraulis eggs, we found that P. engraulis eggs are cyan with faint yellow in color, spheri- cal, telolecithal and non-adhesive. The egg membrane is smooth with good transmittance, average egg membrane diameter was （5.44±0.05） mm, average egg diameter was （1.61 ±0.03 ） mm and the average total length of newly hatched P. engraulis larvae was （5.07 ±0.07 ） mm.