Elusive Giant Invaders: A qPCR‐Based eDNA Survey for Detecting the Introduced Clown Featherback (Notopteridae; <scp><i>Chitala ornata</i></scp>) in a Tropical Riverine System

ABSTRACT The consequences of biological invasions are often difficult to mitigate because it is challenging to extirpate invasive alien species (IAS) once they have established and spread in a new environment. Conservation actions to control IAS populations at early stages of introduction may help prevent invasions, but they need to be guided by efficient detection tools. Here, we examined the possibility of using a species‐specific qPCR‐based eDNA method to detect the clown featherback (Teleostei; Notopteridae; Chitala ornata ) in the Perai River, Peninsular Malaysia. Chitala ornata is a large, tropical, piscivorous freshwater fish species native to mainland Southeast Asia, which is believed to have been recently introduced into the Perai River drainage. We detected the eDNA of C. ornata at three out of the five surveyed sampling points, whereas recent specimen‐based records indicate a widespread distribution. We discuss three potential causes for this partial eDNA detection: (1) the selection of the methodological variables of the qPCR survey, (2) the impact of tropical environmental parameters such as high water temperature and UV exposure and (3) the role of biological factors such as population size and/or seasonal migratory movements of C. ornata possibly linked to its reproductive behaviour. Although qPCR‐based eDNA methods offer several advantages over traditional methods for detecting rare species, multiple methodological and environmental factors can affect the outcomes of qPCR‐based eDNA studies, especially in tropical environments.