Data from: Attracting Common Carp to a bait site with food reveals strong positive relationships between fish density, feeding activity, environmental DNA, and sex pheromone release that could be used in invasive fish management

Measurement of environmental DNA (eDNA) is becoming a common technique to survey for rare and invasive fish due to its sensitivity and specificity. However, its utility is limited by an incomplete understanding of factors governing its sources and fates. Failure to detect eDNA is especially difficult to interpret so surveillance techniques often collect large numbers of samples across broad regions. If, however, fish could be reliably attracted to a single location where their eDNA could be easily measured that would be useful. We conducted a proof‐of‐concept study of this idea using invasive Common Carp. We monitored the distribution of radio‐tagged Carp and their eDNA across a 67 ha lake focusing at the bait site while a pheromone (Prostaglandin F2α; PGF2α) was also measured to determine their reproductive condition. Prior to baiting, Carp were patchily distributed and while eDNA was occasionally detectable, it was patchy and only loosely associated with moderately dense groups of fish. Further, neither Carp, nor their eDNA were consistently measurable at the bait site and surrounding region, and the pheromone was not measurable at all. However, once baiting commenced, Carp started visiting the bait site and feeding, especially at night, where eDNA levels increased 500‐fold as fish densities doubled and PGF2α became detectable. Fish presence, eDNA and pheromone concentrations peaked at night after 6 days, strongly suggesting feeding activity was the main driver. While the presence of eDNA precisely coincided with this aggregation, levels had dropped dramatically within 5 m. PGF2α levels dropped less rapidly and demonstrated the presence of live mature fish. We suggest that food could be used to train fish to come to locations where they otherwise are too scarce to be reliably measured, increasing their eDNA release, making them measurable, and their reproductive condition also discernable by measuring pheromones.

环境DNA（environmental DNA, eDNA）检测凭借其高灵敏度与特异性，正成为珍稀及入侵鱼类调查的常用技术。然而，该技术的应用仍受限于对其来源与去向相关调控因素的认知不足。无法检出eDNA的情形尤为难以解读，因此现有监测手段通常需在大范围区域内采集大量样本。但若可将鱼类可靠诱集至单一地点，使其eDNA便于检测，则将具备极高应用价值。我们以入侵物种普通鲤鱼（Common Carp）为研究对象，开展了该构想的概念验证研究。我们在一处面积为67公顷的湖泊中，以饵料投放点为核心监测了无线电标记普通鲤鱼的分布及其eDNA水平，同时检测信息素前列腺素F2α（Prostaglandin F2α; PGF2α）以判断鲤鱼的生殖状态。投饵前，普通鲤鱼呈斑块状分布；虽偶可检出eDNA，但该物质同样呈斑块状分布，仅与中等密度的鱼群存在弱相关性。此外，饵料点及周边区域始终无法稳定检出鲤鱼及其eDNA，亦未检测到目标信息素。但投饵启动后，普通鲤鱼开始造访饵料点并觅食，尤其活跃于夜间。随着鱼群密度翻倍，eDNA水平提升500倍，同时可检测到PGF2α。投饵6天后的夜间，鱼类存在情况、eDNA与PGF2α浓度均达到峰值，强烈表明觅食活动是该现象的主要驱动因素。尽管eDNA的检出与该鱼群聚集行为精准吻合，但eDNA水平在距离饵料点5米范围内便急剧下降。PGF2α的水平下降速度则相对缓慢，可证明区域内存在活体成熟个体。我们认为，可利用食物将鱼类诱集至原本因密度过低而难以可靠检测的地点，提升其eDNA释放量以实现有效检测，同时通过检测信息素判断其生殖状态。