Fishes stocked for recreation and angling can damage freshwater habitats and negatively impact biodiversity. The pond-associated crucian carp (Carassius carassius) is rare across Europe and is stocked for conservation management in England, but its impacts on pond biota are understudied. Freshwater invertebrates contribute substantially to aquatic biodiversity, encompassing many rare and endemic species, but their small size and high abundance complicate their assessment. Practitioners have employed sweep-netting and kick-sampling with microscopy (morphotaxonomy), but specimen size/quality and experience can bias identification. DNA and environmental DNA (eDNA) metabarcoding offer alternative means of invertebrate assessment. We compared invertebrate diversity in ponds (N = 18) with and without crucian carp using morphotaxonomic identification, DNA metabarcoding and eDNA metabarcoding. Five 2 L water samples and 3 min sweep-net samples were collected at each pond. Inventories produced by morphotaxonomic identification of netted samples, DNA metabarcoding of bulk tissue samples and eDNA metabarcoding of water samples were compared. Alpha diversity was greatest with DNA or eDNA metabarcoding, depending on whether standard or unbiased methods were considered. DNA metabarcoding reflected morphotaxonomic identification, whereas eDNA metabarcoding produced markedly different communities. These complementary tools should be combined for comprehensive invertebrate assessment. Crucian carp presence minimally reduced alpha diversity in ponds, but positively influenced beta diversity through taxon turnover (i.e., ponds with crucian carp contained different invertebrates to fishless ponds). Crucian carp presence contributes to landscape-scale invertebrate diversity, supporting continued conservation management in England. Our results show that molecular tools can enhance freshwater invertebrate assessment and facilitate development of more accurate and ecologically effective pond management strategies.

中文翻译：

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评估受威胁的鲫鱼 (Carassius carassius) 对池塘无脊椎动物多样性的影响：传统工​​具和分子工具的比较

为娱乐和垂钓而放养的鱼类会破坏淡水栖息地并对生物多样性产生负面影响。与池塘相关的鲫鱼 ( Carassius carassius ) 在欧洲很少见，在英国被放养用于保护管理，但其对池塘生物群的影响尚未得到充分研究。淡水无脊椎动物对水生生物多样性做出了重大贡献，包括许多稀有和特有物种，但它们的体型小和丰度高，使它们的评估复杂化。从业者已经使用显微镜（形态分类学）进行扫网和踢样采样，但样本大小/质量和经验可能会导致识别偏差。DNA 和环境 DNA (eDNA) 元条形码提供了无脊椎动物评估的替代方法。我们比较了池塘中的无脊椎动物多样性 ( N = 18) 使用形态分类学鉴定、DNA metabarcoding 和 eDNA metabarcoding 使用和不使用鲫鱼。在每个池塘收集 5 个 2 L 水样和 3 分钟清扫网样品。比较了网状样品的形态分类学鉴定、大量组织样品的 DNA 元条形码和水样的 eDNA 元条形码所产生的清单。DNA 或 eDNA 元条形码的 Alpha 多样性最大，这取决于是否考虑标准方法或无偏见方法。DNA metabarcoding 反映了形态分类学的鉴定，而 eDNA metabarcoding 产生了明显不同的群落。这些补充工具应结合起来进行综合无脊椎动物评估。鲫鱼的存在最小程度地降低了池塘中的 alpha 多样性，但通过分类群周转对 beta 多样性产生了积极影响（即，有鲫鱼的池塘含有不同的无脊椎动物和无鱼的池塘）。鲫鱼的存在有助于景观尺度的无脊椎动物多样性，支持英格兰的持续保护管理。我们的结果表明，分子工具可以增强淡水无脊椎动物的评估，并促进制定更准确和生态有效的池塘管理策略。