Advancing early detection technologies for Dreissena polymorpha (Pallas, 1771): comparing mussel detection in environmental samples with environmental DNA (eDNA) and detection canines

Early detection and rapid response represent cornerstones of effective management of biological invasions, and development of methods that increase the sensitivity and efficiency of species detection directly benefit such efforts. We compared environmental DNA (eDNA) and canine scent detection of Dreissena polymorpha (Pallas, 1771), the Eurasian zebra mussel, in lakes of central Texas, USA. Environmental DNA analysis has become routinely incorporated as a component of D. polymorpha management programs; however, canine scent detection has typically been limited to inspection for adult mussels on watercraft. Thus, our work represents the first attempt to evaluate detection of D. polymorpha veligers (i.e., free-swimming larval stages) and other microscopic traces in environmental samples with canine scent detection. The specific objectives of this study were to: 1) evaluate whether canines can detect D. polymorpha in environmental samples; 2) quantify and compare limits of detection of canine scent detection and eDNA analysis; and 3) assess the performance of detection technologies through blind screening of ten lakes. In order of objective, our major findings include: 1) canines can be trained to detect D. polymorpha veligers in water samples; 2) eDNA detection is 2-1 OOx more sensitive than canine scent detection; and 3) canine scent detection and eDNA both appear to outperform microscopy for D. polymorpha detection in environmental water samples. However, more work is needed to understand the conditions dictating when canine scent detection or eDNA outperforms the other.