A myriad of factors affect stream fish assemblages, and most of them are intimately regulated by surrounding land uses. One of the most pernicious impacts on streams is the release of urban effluents. Accordingly, understanding the fish assemblage patterns as well as the environmental drivers that modulate them in the context of urban streams which also are exposed to other land uses is mandatory. We evaluated the longitudinal patterns of fish assemblages in an urbanised Neotropical prairie stream exposed to downstream patches of different surrounding land uses. Several variables of water quality, in-stream habitat and riparian corridors were measured, and their relationships with fish metrics were explored. A fish metric selection protocol was implemented, and several multivariate analyses were used. Three main patterns of fish response were observed. Assemblage-level attributes as diversity, richness, biomass, number of families and trophic guilds and proportion of Characiformes and intolerant species were responsive to the natural gradient in habitat (pools) and riparian (riparian width) conditions expected in non-impacted lotic ecosystems. Conversely, a downstream continuum of recovery in water quality (dissolved oxygen, conductivity, NO3:NH4 and bacteriological loads) and habitat structure (sediment depth) would influence the distribution of fish species regarding their environmental tolerance and habitat preferences. Finally, local habitat aspects (nitrites, submerged macrophytes, bare soil cover and bank incisions by livestock) seemed relevant for the trophic structure (omnivorous species) of fish assemblages. A complex natural and anthropic longitudinal scenario together with local disruptions imposed by surrounding land uses were directive for fish.

中文翻译：

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暴露于多种自然和人为因素的新热带城市化草原溪流中的鱼类群落结构

无数因素影响河流鱼类群落，其中大多数受到周围土地利用的密切调节。对河流最有害的影响之一是城市污水的排放。因此，必须了解鱼类聚集模式以及在城市河流背景下调节它们的环境驱动因素，这些河流也暴露于其他土地用途。我们评估了城市化的新热带草原溪流中鱼类组合的纵向模式，该溪流暴露于不同周围土地利用的下游斑块。测量了水质、河流栖息地和河岸走廊的几个变量，并探讨了它们与鱼类指标的关系。实施了鱼指标选择协议，并使用了几种多变量分析。观察到鱼类反应的三种主要模式。多样性、丰富度、生物量、科和营养行会的数量以及 Characiformes 和不耐受物种的比例等组合级属性对未受影响的生态系统中预期的栖息地（水池）和河岸（河岸宽度）条件的自然梯度作出反应。相反，水质（溶解氧、电导率、NO3:NH4 和细菌负荷）和栖息地结构（沉积物深度）的下游连续恢复将影响鱼类在环境耐受性和栖息地偏好方面的分布。最后，当地栖息地方面（亚硝酸盐、沉水植物、裸露的土壤覆盖和牲畜的堤岸切口）似乎与鱼类组合的营养结构（杂食性物种）有关。