Headwater streams play an essential role in catchment ecosystem processes and are particularly vulnerable to land use degradation and anthropic hydrological alterations. Considering that fish assemblages are reliable indicators of the ecological integrity of streams, we evaluated the ichthyofauna structure in four headwater Pampean streams located at catchment areas with contrasting land uses and hydrological man-made alterations. During autumn and spring of 2017 and 2018, fish assemblages were sampled and physicochemical and water table depth were measured. Specific richness, abundance, and diversity of fish assemblages were estimated. The degree of anthropic intervention of drainage networks and wetland coverage was estimated for each catchment. Statistical analyses assessed the differences between rural and periurban sampling sites in terms of environmental variables and fish assemblage structure, as well as the relationships between the biotic and abiotic variables. Results showed differences among headwater streams according to their land uses, hydrological alterations, and fish assemblage structure, evidencing a combined effect of land use and hydrologic alterations on fish assemblage. Changes in these communities can reflect not only alterations in water quality caused by local land use but also the influence of the catchment environmental integrity related to hydrological modifications and other phenomena that can occur simultaneously and at different geographical scales.

源头溪流在流域生态系统过程中发挥着重要作用，特别容易受到土地利用退化和人为水文变化的影响。考虑到鱼类组合是河流生态完整性的可靠指标，我们评估了位于集水区的四个源头水源 Pampean 河流中的鱼群结构，这些河流位于集水区，土地利用和水文人为改变形成鲜明对比。在 2017 年和 2018 年秋春季，对鱼类组合进行了采样，并测量了理化和地下水位深度。估计了鱼类组合的具体丰富度、丰度和多样性。估计每个流域的排水网络和湿地覆盖的人为干预程度。统计分析评估了农村和城郊采样点在环境变量和鱼类组合结构方面的差异，以及生物和非生物变量之间的关系。结果表明，根据土地利用、水文变化和鱼类组合结构，上游河流之间存在差异，证明土地利用和水文变化对鱼类组合的综合影响。这些社区的变化不仅可以反映由当地土地使用引起的水质变化，还可以反映与水文变化相关的集水区环境完整性的影响以及可能在不同地理范围同时发生的其他现象。以及生物和非生物变量之间的关系。结果表明，根据土地利用、水文变化和鱼类组合结构，上游河流之间存在差异，证明土地利用和水文变化对鱼类组合的综合影响。这些社区的变化不仅可以反映由当地土地使用引起的水质变化，还可以反映与水文变化相关的集水区环境完整性的影响以及可能在不同地理范围同时发生的其他现象。以及生物变量和非生物变量之间的关系。结果表明，根据土地利用、水文变化和鱼类组合结构，上游河流之间存在差异，证明土地利用和水文变化对鱼类组合的综合影响。这些社区的变化不仅可以反映由当地土地使用引起的水质变化，还可以反映与水文变化相关的集水区环境完整性的影响以及可能在不同地理范围同时发生的其他现象。