Long-term effects of a rural landscape on the structure and trophic organization of a fish assemblage

Abstract Aim We investigated the long-term effects of a rural landscape on the structure and trophic organization of a fish assemblage. Methods We compared environmental data and data from fish assemblage structure and trophic organization sampled in a stream located in a rural area, within a time gap of 20 years. Results We observed only punctual changes in the environmental variables and fish structure, which may not be related to the rural landscape. In fish diet, insectivory remained predominant in all sample periods. However, when we analyzed the groups of hexapods consumed by the fish species, we found a substitution of Ephemeroptera and Trichoptera by Diptera over time. Conclusions Although the fish assemblage structure was not affected, the insectivore diet analysis showed that the stream stretch could be in an ongoing process of environmental quality loss, once the simplification in the macroinvertebrates assemblage structure over time is indicative of environmental degradation.

摘要：本研究旨在探究乡村景观对鱼类集合群（fish assemblage）的结构与营养结构（trophic organization）的长期影响。方法：我们对比了间隔20年于某乡村溪流采集的环境数据、鱼类群落结构及营养结构数据。结果：仅观察到环境变量与鱼类群落结构存在零星变化，且此类变化或与乡村景观无关；在鱼类食性方面，食虫性在所有采样时期均占主导地位，但进一步分析鱼类所摄食的六足类动物（hexapods）类群时，发现随时间推移，蜉蝣目（Ephemeroptera）与毛翅目（Trichoptera）类群被双翅目（Diptera）类群取代。结论：尽管鱼类集合群结构未受显著影响，但食性分析结果表明，该溪流河段或正处于环境质量退化的进程中——因大型无脊椎动物群落（macroinvertebrates assemblage）的结构随时间发生简化，这一现象是环境退化的指示标志。