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Fish assemblage changes in relation to watershed landuse disturbance

机译：与流域土地利用扰动有关的鱼群变化

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Fish assemblage collections were assessed in sub-watersheds containing various land use types to relate overall biotic condition to patterns of watershed disturbance and to the influence of introduced fishes. Four hundred historical and contemporary fish collections were analyzed in conjunction with land use and land cover data among 200, first- through fourth-order sub-watersheds across Pennsylvania. A high degree of collinearity among several land use types and the presence of non-indigenous fishes was determined, indicating multiple anthropogenic influences. Significant relationships were found between various land me types and the Jaccard coefficient of similarity, the primary index used to evaluate changes between fish collections, across all major drainages. In general, the Jaccard coefficient of similarity increased to a value of one as the percentage of forested land increased, while the Jaccard coefficient of similarity decreased as percentages of agricultural and urban land increased. Sub- watersheds that showed declines in species richness had significantly higher percentages of agricultural and developed land, while those sub-watersheds with higher amounts of forested land appeared relatively stable. Seventy-percent of those species that experienced declines were either insectivores or henthic insectivores. The largest increases among the fish guilds occurred within the insectivore-piscivore group. We conclude that land use influences at the sub-watershed scale and the introduction of non-indigenous fishes have had a significant influence on fish community composition.
机译：在包含各种土地利用类型的小流域中评估了鱼类的集合，以将总体生物状况与流域扰动的模式以及引进鱼类的影响联系起来。结合宾夕法尼亚州200个一阶至四阶子流域中的土地利用和土地覆盖数据，分析了400种历史和现代鱼类资源。确定了几种土地利用类型之间的高度共线性和非土著鱼类的存在，表明存在多种人为影响。发现各种土地类型与Jaccard相似系数之间的重要关系，Jaccard相似系数是用于评估所有主要排水系统中鱼品收集之间变化的主要指标。通常，随着林地百分比的增加，雅克卡相似度系数增加到1，而随着农业和城市土地的百分比增加，雅克卡相似度系数降低。物种丰富度下降的小流域的农业和发达土地所占比例明显更高，而林地数量较多的那些小流域则显得相对稳定。在经历衰退的物种中，有百分之七十是食虫性或肉食性食虫性。在鱼类行会中增幅最大的是食虫食肉动物群。我们得出的结论是，土地利用在小流域范围内的影响以及非土著鱼类的引进对鱼类群落组成具有重大影响。

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