三峡水库小江流域常见鱼类肌肉碳、氮、磷生态化学计量特征

为探究三峡水库小江流域常见草食性、浮游生物食性、肉食性和杂食性鱼类肌肉的碳（C）、氮（N）、磷（P）生态化学计量特征，2018年1月（枯水期）和7月（丰水期）在小江流域7个设定断面，采集4种食性的鱼类样品，测定其生长特性指标，分析鱼类肌肉C、N、P生态化学计量特征及相关性。结果表明，鱼类肌肉C、N、P元素含量为34.75%~58.71%、 7.00%~15.45%、0.89%~8.21%，C:N、C:P和N:P为3.62~9.75、16.92~136.95、2.14~35.31，其中磷元素含量变化最大且是导致N:P变化的主要原因。小江流域不同食性鱼类肌肉元素组成差异不明显，其中仅草食性鱼类、浮游生物食性鱼类 的N含量和N:P显著大于肉食性鱼类和杂食性鱼类（P<0.05），其他元素及比例在各食性鱼类之间均无显著性差异（P>0.05）；不同采样断面的鱼类肌肉元素含量及比例无显著性差异（P<0.05）；相关性分析发现，小江流域鱼类肌肉N和 P含量呈负相关关系（P<0.05），除草食性外，各食性鱼类的N含量均与水体NO-3-N含量呈显著正相关（P<0.05）。研究结果对深入了解大坝干扰下水生态系统食物网营养关系及营养循环格局具有重要意义。

The C:N:P Ratio in Muscle Tissue of Fish from Xiaojiang River

In this study, we explored the stoichiometric ratios of carbon (C), nitrogen (N) and phosphorous (P) in the muscle tissue from common herbivorous, planktonic-feeding, carnivorous and omnivorous fish in Xiaojiang River of Three Gorges Reservoir (TGR) and analyzed their relationship with the nutrient status of the water body. In January (dry season) and July (wet season) of 2018, fish with the four diets were collected from 7 sampling sections in Xiaojiang River. The growth parameters of the specimens were measured in situ and the C, N and P levels and their ratios in muscle tissues were determined. Water samples were collected simultaneously for the determination of water environmental parameters. A total of 325 individuals from 14 species were collected during the survey. The tissue C, N and P concentration ranges in muscle tissue of the four feeding groups were, respectively, 34.75%-58.71%, 7.00%-15.45% and 0.89%-8.21%, and the respective ratio ranges of C:N, C:P and N:P were 3.62-9.75, 16.92-136.95 and 2.14-35.31. The most variable component was P content, which was the main cause of variation in the N:P ratio. The N levels and N:P ratios of herbivorous and plankton-feeding fish were significantly higher than those in carnivorous and omnivorous fish (P<0.05), but there were no significant differences between other elements and propor? tions among fish species with different diets (P>0.05). Nor were there any significant differences in the element content or proportions among the fish collected from different sampling sections. Correlation analysis shows that N and P levels in fish from Xiaojiang River were negatively correlated with each other (P<0.05) and, except for herbivorous fish, there was a significant positive correlation be? tween N content and the NO-3-N content of the water (P<0.05). It is important to understand the relationship of different nutrients in the food web of aquatic ecosystems and our results provide a better understanding of these relationships in an aquatic ecosystem impacted by a dam.