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，正成为珍稀与入侵鱼类调查的主流技术之一。然而，当前学界对调控eDNA来源与归宿的相关因素认知尚不完整，限制了该技术的应用效能。无法检出eDNA的情况尤其难以解读，因此相关监测工作通常需在大范围区域内采集大量样本。但若能将鱼类可靠诱集至单一地点，以便便捷检测其eDNA，则将具备极高的应用价值。
我们以入侵性普通鲤（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67公顷的湖泊中，监测了射频标记鲤的分布及其eDNA水平，监测重点为诱饵投放点区域，同时检测信息素（前列腺素F2α, Prostaglandin F2α; PGF2α）以判定鲤的生殖状态。
在投放诱饵前，鲤的分布呈斑块状；尽管偶尔可检出eDNA，但其分布同样呈斑块状，仅与中等密度的鱼群存在微弱关联。此外，诱饵点及周边区域均无法稳定检出鲤及其eDNA，且未检测到信息素。
然而，诱饵投放启动后，鲤开始造访诱饵点并觅食，尤其在夜间活动；随着鱼群密度翻倍，eDNA水平升高500倍，同时可检测到信息素。6天后，鱼类存在情况、eDNA浓度与信息素水平均在夜间达到峰值，强烈表明觅食活动是该现象的主要驱动因素。
尽管eDNA的检出结果与该鱼群聚集现象精准吻合，但eDNA水平在距离诱饵点5米范围内便出现大幅下降。信息素水平的下降速度则相对平缓，可佐证活体成熟鲤的存在。
我们认为，可利用食物将鱼类诱集至原本因种群密度过低而难以稳定检测的区域，通过提升eDNA释放量使其可被检出，同时通过检测信息素以判断其生殖状态。