A major issue for water resource management is the assessment of environmental degradation of lotic ecosystems. The overall aim of this study is to develop a multi-metric fish index for the cyprinid streams of the Caspian Sea Basin (MMICS) in Iran. As species diversity and composition as well as population structure in the studied streams are different to other regions, there is a substantial need to develop a new fish index. We sampled fish and environmental data of 102 sites in medium sized streams. We analysed human pressures at different spatial scales and determined applicable fish metrics showing a response to human pressures. In total, five structural and functional types of metrics (i.e. biodiversity, habitat, reproduction, trophic level and water quality sensitivity) were considered. In addition, we used 29 criteria describing major anthropogenic human pressures at sampling sites and generated a regional pressure index (RPI) that accounted for potential effects of multiple human pressures. For the MMICS development, we first defined reference sites (least disturbed) and secondly quantified differences of fish metrics between reference and impaired sites. We used a Generalised Linear Model (GLM) to describe metric responses to natural environmental differences in least disturbed conditions. By including impaired sites, the residual distributions of these models described the response range of each metric to human pressures, independently of natural environmental influence. Finally, seven fish metrics showed the best ability to discriminate between impaired and reference sites. The multi-metric fish index performed well in discriminating human pressure classes, giving a significant negative linear response to a gradient of the RPI. These methods can be used for further development of a standardised monitoring tool to assess the ecological status and trends in biological condition for streams of the whole country, considering its complex and diverse geology and climate.

中文翻译：

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伊朗里海盆地鲤科鱼类新的多指标评估指数

水资源管理的一个主要问题是对水生态系统环境退化的评估。本研究的总体目标是为伊朗里海盆地 (MMICS) 的鲤科鱼类制定多指标鱼类指数。由于所研究河流中的物种多样性和组成以及种群结构与其他地区不同，因此迫切需要制定新的鱼类指数。我们在中等规模的溪流中对 102 个地点的鱼类和环境数据进行了采样。我们分析了不同空间尺度的人类压力，并确定了显示对人类压力的反应的适用鱼类指标。总共考虑了五种结构和功能类型的指标（即生物多样性、栖息地、繁殖、营养水平和水质敏感性）。此外，我们使用了 29 项标准来描述采样地点的主要人为人类压力，并生成了一个区域压力指数 (RPI)，以说明多种人类压力的潜在影响。对于 MMICS 开发，我们首先定义参考站点（最少干扰），然后量化参考站点和受损站点之间鱼类指标的差异。我们使用广义线性模型 (GLM) 来描述在最少干扰条件下对自然环境差异的度量响应。通过包括受损站点，这些模型的残差分布描述了每个指标对人类压力的响应范围，与自然环境影响无关。最后，七个鱼类指标显示了区分受损和参考站点的最佳能力。多度量鱼指数在区分人类压力类别方面表现良好，对 RPI 的梯度给出了显着的负线性响应。考虑到其复杂多样的地质和气候，这些方法可用于进一步开发标准化的监测工具，以评估全国河流的生态状况和生物状况的趋势。