ABSTRACT

Many river networks in southern Europe are intermittent. In summer, the surface flow is zero and many streams become isolated pools. In this study, 128 dry season pools were studied covering first- to fourth-order streams on the Degebe River network (south Portugal). The aim of the study was to identify pool types based on environmental drivers and conditions and fish assemblages. In summer, dry streambed area exceeded 50% in all reaches and 95% in headwater sections. The pool features were primarily shaped by their location in the river network, which determined the pool morphology and the structure of fish assemblages. Pool sizes increased from upstream to downstream, as did species richness and diversity. Pools in upstream reaches were dominated by small native fishes while the larger-sized individuals tended to occupy deeper, larger, and more persistent pools. Smaller pools in downstream reaches were dominated by non-native species, which may be related to habitat preferences and minimization of negative interactions between native and non-native species. Because dry season pools represent key habitats in intermittent streams, conservation programs should be designed to reduce human pressures and improve hydromorphological heterogeneity and water quality, taking into account the natural patterns of pool types at regional and local scales.

摘要

南欧的许多河网都是断断续续的。在夏季，地表流量为零，许多水流变成孤立的水池。在这项研究中，研究了128个旱季水池，这些水池覆盖了Degebe河网（葡萄牙南部）的一阶到四阶流。这项研究的目的是根据环境驱动因素和条件以及鱼类的种类确定水池类型。夏季，所有河段的干流河床面积均超过50％，上游水域的干流床面积均超过95％。池的特征主要是由它们在河网中的位置决定的，这决定了池的形态和鱼群的结构。库的大小从上游到下游增加，物种丰富度和多样性也增加。上游河段的水域以小型本地鱼类为主，而大型个体往往占据更深，更大，和更持久的池。下游河段中较小的水库以非本地物种占主导，这可能与栖息地偏好以及本地物种与非本地物种之间的负面互动最小化有关。由于枯水期池代表间歇性河流中的关键栖息地，因此应设计保护方案，以减少人为压力并改善水文形态异质性和水质，同时考虑到区域和地方规模的池型自然模式。