1. Conservation of riverine fish often aims to improve access to spawning grounds and restore longitudinal connectivity by removing migration barriers, and involves substantial investments. However, these investments also enable non‐native predators to invade upstream into spawning areas and potentially adversely affect the recruitment of threatened freshwater fish through egg or fry predation.
2. Detecting egg predation is often challenging. Visual inspections of fish gut contents may underestimate predation of soft materials such as eggs and fry, which limits the discovery of predators preying upon these life‐stages. DNA‐based detection assays may offer a more sensitive tool to assess predation of soft materials.
3. A conservation issue was confirmed by developing and applying a species‐specific DNA‐based detection assay: invasive round goby (Neogobius melanostomus) prey on the eggs or fry of the threatened common nase (Chondrostoma nasus) in Switzerland.
4. DNA‐based detection assays were also developed for five other valuable native fish species, including endangered salmonid and cyprinid river spawners. The applicability of the assays was confirmed in a series of laboratory and field feeding experiments involving eggs and fish tissue. In addition, this work provides a guiding framework for conservation managers regarding the use and applicability of different DNA‐based detection approaches for gut content analysis.
5. The results of this study could inform local conservation measures – such as temporary reductions in the density of round goby at spawning sites prior to spawning – and demonstrate how targeted application of species‐specific molecular markers may advance freshwater fish management.

中文翻译：

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通过物种特异性肠内含物DNA分析揭示侵入性虾虎鱼对本地鱼卵的捕食

1. 保护河上鱼类通常旨在通过消除迁徙障碍来改善对产卵场的访问并恢复纵向连通性，并涉及大量投资。但是，这些投资还使非本地捕食者能够向上游侵入产卵区，并可能对通过捕食卵或鱼苗而捕捞受威胁的淡水鱼产生不利影响。
2. 检测鸡蛋的捕食通常具有挑战性。目视检查鱼肠内容物可能会低估诸如鸡蛋和鱼苗之类的软物质的捕食，这限制了捕食捕食这些生命阶段的天敌。基于DNA的检测方法可能提供一种更敏感的工具来评估软物质的捕食。
3. 通过开发和应用基于物种的特定于DNA的检测方法，确认了一个保护问题：在瑞士，侵袭性圆形虾虎鱼（Neogobius melanostomus）捕食受威胁的普通酶（Chondrostoma nasus）的卵或鱼苗。
4. 还开发了基于DNA的检测方法用于其他五种有价值的本地鱼类，包括濒临灭绝的鲑鱼和塞浦路斯河产卵卵。在涉及鸡蛋和鱼组织的一系列实验室和田间饲养实验中证实了该测定法的适用性。此外，这项工作为保护管理者提供了有关肠道内容分析的不同基于DNA的检测方法的使用和适用性的指导框架。
5. 这项研究的结果可以为当地的保护措施提供信息-例如在产卵前暂时降低产卵地点的圆虾虎鱼密度-并证明针对物种的特定分子标记物的定向应用可如何促进淡水鱼的管理。