【摘要】 为了解长江中上游鲌属鱼类种群动态和种间营养关系,本研究利用碳、氮稳定同位素分析技术,对来自长江中上游3个区域的达氏鲌（Culter dabryi）、蒙古鲌（Culter mongolicus）和翘嘴鲌（Culter alburnus）样品的碳、氮稳定同位素特征和营养生态位进行比较分析。结果显示, 3种鲌的δ¹³C值在各区域均有显著性差异（P<0.05）,而δ¹⁵N值仅在上游江段差异显著（P<0.05）,表明三者间食物来源和营养级位置存在空间上的差异。多营养生态位指标结果显示,在长江中上游,蒙古鲌的食物来源更为广泛,占据的营养生态位空间总量较大,且在大多数情况下,蒙古鲌的生态位宽度大于达氏鲌和翘嘴鲌,这可能与蒙古鲌独特的摄食器官有关。3种鲌在长江中上游各江段的食性竞争存在差异,其中,蒙古鲌与翘嘴鲌、达氏鲌的重叠度相对较高,而翘嘴鲌与达氏鲌之间重叠度较低甚至无重叠,表明在长江中上游水域,蒙古鲌由于对不同饵料资源的利用能力强而易与其他两者出现食性竞争,而翘嘴鲌与达氏鲌因对各自优势饵料的摄食偏好性强,在食物资源维度上出现了一定的生态位分化。更多还原

【Abstract】 Culter species, as carnivorous fishes in lakes and reservoirs in the middle and upper reaches of the Yangtze River, usually play the top predator role in the freshwater ecosystem. Culter dabryi, Culter mongolicus,and Culter alburnus are the most common and abundant Culter species in these regions. Because of sympatry and predatory habits, these Culter species seemingly have interspecific resources competition, which could be fierce especially when food resources are limited. In addition, the changes in their population could have an important impact on other fish species or communities through top-down effects. To understand the interspecific trophic relationships of Culter in the middle and upper reaches of the Yangtze River, carbon and nitrogen stable isotope analysis technology and isotope-derived metrics were used to examine stable isotope characteristics and trophic interrelations of these three Culter species samples from the upper reaches, reservoir reaches, and the middle reaches. A one-way analysis of variance（ANOVA） was used to test whether there were significant differences in δ¹³C and δ¹⁵N values among the three Culter species in each river section. Six quantitative metrics in the bi-plot space, including δ¹³C range（CR）, δ¹⁵N range（NR）, mean distance to centroid（CD）, mean nearest neighbor distance（MNND）, standard deviation of the nearest neighbor distance（SDNND）, and total area（TA） derived from stable isotope data, were used to describe trophic niche space, trophic diversity, and redundancy. Instead of total area（TA）, which is highly sensitive to sample size, standard ellipse area（SEA） was also used to quantify the trophic niche space of each species. Besides, to provide more robust metrics and allow for statistical comparisons among sites and species, Bayesian methodology was implemented to generate a posterior distribution of estimates of these metrics. The results showed that δ¹³C values of the three Culter species differed significantly（P<0.05） in each region, while the significant disparity of δ¹⁵N values only appeared in the upper reaches of the river（P<0.05）,indicating that there were spatial differences in the food sources and trophic levels among the three species. The results of multi-trophic ecological niche indicators showed that C. mongolicus had the highest SEAB（Bayesian standard ellipse area） values in all river sections, and the probability of its SEAB being greater than the SEAB values of the other two Culter species ranged from 74.7% to 96.4%. Additionally, the Bayesian results of the CR,CD, and MNND indicators were also highest in the middle and upper reaches of the Yangtze River, indicating that C. mongolicus has a wider food source and occupies a larger trophic niche space. In most cases, the niche width of C. mongolicus is larger than those of C. dabryi and C. alburnus, which may be related to the fact that C.mongolicus has a wide mouth end position and a sparse gill rake that facilitates food passage. The results of stable isotope standard ellipse area overlap showed that there were spatial differences in the niche space overlap among three Culter species. Among them, the highest overlap of stable isotope ellipsoidal area（0.522） was found between C. mongolicus and C. alburnus in the midstream, which accounted for 62.4% and 76.3% of the total SEA of each species, respectively. The SEA overlap between C. dabryi and C. alburnus was lower, only about 0.1 in the upper or middle reaches and no overlap was observed in the reservoir area. Generally, the overlaps between C.mongolicus and C. alburnus or C. dabryi were higher than other pairwise comparisons. These results indicated that C. mongolicus are more liable to have feeding competition with the other two Culter species in the middle and upper reaches of the Yangtze River. Nevertheless, there appeared a certain niche differentiation of food resources between C. alburnus and C. dabryi due to their preference for feeding on their dominant food.更多还原