Fish–habitat relationships are a key element for conservation and management strategies, especially in highly disturbed areas where fish communities are subjected to many human pressures. In this regard, multiscale studies help to improve the knowledge of the spatial components and identify local (e.g. water width) and regional (e.g. elevation) key variables in species distribution. We examined local and regional requirements to study freshwater fish assemblage and occurrence at 216 locations in a highly disturbed basin, the Guadalquivir River Basin (S Spain). Fifteen environmental variables were considered at local scale and twenty at regional level. A total of eighteen species were captured during field sampling. The global prevalence for introduced species was 25%, which can be considered a high value. The most extended introduced species were eastern mosquitofish (Gambusia holbrooki) and pumpkinseed (Lepomis gibbosus), with around 10% prevalence. Regional and local scales showed different relevance according to the level-study approach (community or species). At the community level, the local, regional and shared components revealed similar influence on the fish assemblage, while at individual species level the local component was the main factor to explain most of fish occurrences. Moreover, variables’ interaction was scarcely selected and almost no introduced species distribution was affected by the interaction of any variable. Our results highlight the poor conservation status of the native fish fauna of the Guadalquivir River Basin as well as the importance of analyzing fish–habitat relationships at different scales and approach. These results provide useful information to assess and design conservation strategies in Mediterranean-type basin.

中文翻译：

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在高度受干扰的地中海型流域中对淡水鱼分布的多尺度影响：社区和物种的应对

鱼类与栖息地的关系是保护和管理战略的关键要素，特别是在鱼类社区遭受许多人为压力的高度动荡地区。在这方面，多尺度研究有助于提高对空间成分的认识，并确定物种分布中的局部（例如水宽）和区域（例如海拔）关键变量。我们研究了当地和区域性要求，以研究在一个受严重扰动的盆地瓜达基维尔河盆地（西班牙）的216个地点的淡水鱼的组装和发生。在地方一级考虑了15个环境变量，在区域一级考虑了20个环境变量。在田间采样中总共捕获了18种。外来物种的全球流行率为25％，可以认为是很高的价值。Gambusia holbrooki）和南瓜子（Lepomis gibbosus），患病率约为10％。根据级别研究方法（社区或物种），区域和地方尺度显示出不同的相关性。在社区一级，本地，区域和共享部分对鱼类的聚集显示出相似的影响，而在单个物种一级，本地部分是解释大多数鱼类发生的主要因素。此外，几乎没有选择变量的相互作用，并且几乎没有引入的物种分布受到任何变量相互作用的影响。我们的结果强调了瓜达尔基维尔河流域本地鱼类区系的保护状况不佳，以及分析不同规模和方法的鱼类－栖息地关系的重要性。这些结果为评估和设计地中海型盆地的保护策略提供了有用的信息。