Environmental DNA (eDNA) detection of aquatic invasive species using quantitative polymerase chain reaction (qPCR) is a powerful tool for resource managers, but qPCR has traditionally been confined to laboratory analysis. Laboratory results often take days or weeks to be produced, limiting options for rapid management response. To circumvent laboratory delay, we combined a purpose‐built eDNA filtration system (Smith‐Root eDNA‐Sampler) with a field DNA extraction and qPCR analysis platform (Biomeme) to form a complete field eDNA sampling and detection process. A controlled laboratory study involving serial dilutions of New Zealand mudsnail (Potamopyrgus antipodarum; Gray, 1843) eDNA was conducted to compare the detection capabilities of the field system with traditional bench qPCR. Additionally, field validation studies were conducted to determine whether field eDNA analysis can be used to map mudsnail eDNA distribution and quantify temporal fluctuations. In the laboratory experiment, both qPCR platforms (Biomeme, bench qPCR) lost the ability to reliably detect mudsnail eDNA at the same dilution level, with starting quantity values as low as 21 DNA copies/reaction. A strong linear relationship was observed between the average quantification cycle values of the two platforms (slope = 1.101, intercept = −1.816, R2 = 0.997, p < 0.001). Of the 80 field samples collected, 44 (55%) tested positive for mudsnail eDNA with Biomeme, and results identified both spatial and temporal fluctuations in mudsnail eDNA/L. However, the average qPCR inhibition rate with Biomeme was 28% for field samples, and up to 39% in the temporal dataset. With additional optimization to reduce inhibition, the eDNA‐Sampler/Biomeme system has potential to be a rapid and highly effective detection/quantification tool for aquatic invasive species.

Environmental DNA (eDNA) detection of aquatic invasive species is currently at the forefront of aquatic conservation efforts because the methodology provides a cost effective and sensitive means to detect animals at low densities. Developments in eDNA technologies have improved detection probabilities for rare, indicator, and invasive species over the past decade. However, standard lab analysis can take days or weeks before results are available and is prohibitive when rapid management decisions are required for mitigation. Here, we investigated the performance of a real-time quantitative PCR system for on-site eDNA detection of New Zealand mud snails (Potamopyrgus antipodarum). Six sites in western Washington, USA were sampled using the rapid eDNA technique and traditional methods, with five samples per site. On-site eDNA detection of mud snails resulted in a 10% increase in positive sites (16/30 = 53% positive) relative to visual surveys (13/30 = 43% positive). In addition, positive associations were observed between mud snail eDNA concentration (eDNA copies per reaction) and the number of mud snail individuals at each site (R2 = 0.78). We show that the rapid on-site eDNA technology can be effective for detection and quantification of New Zealand mud snails in freshwaters. This on-site eDNA detection approach could possibly be used to initiate management protocols that allow for more rapid responses during the onset of biological invasions.

7Establishing base-line knowledge of native snails in an area and their relative abundance 8 is important in understanding the role of snails in their environment and the possible use of snails 9 as a bioindicator. This information can also be used to determine how an invasive species is 10 affecting the native populations over time. Six genera of gastropods were found in the wetland 11 ponds of Turnbull National Wildlife Refuge (TNWR) from April to June 2012, including the 12 invasive European ear snail (Radix auricularia) which was found in four lakes it was not 13 previously known to inhabit. A dominant snail genus was found for each lake, with Middle Pines 14 Lake being dominated by Radix auricularia. Conductivity was the only abiotic factor studied that 15 positively correlated with genera richness (p = 0.035). 16 17 18 19 20 21 22 23 24 PeerJ PrePrints | http://dx.doi.org/10.7287/peerj.preprints.555v1 | CC-BY 4.0 Open Access | rec

Establishing base-line knowledge of native snails in an area and their relative abundance is important in understanding the role of snails in their environment and the possible use of snails as a bioindicator. This information can also be used to determine how an invasive species is affecting the native populations over time. Six genera of gastropods were found in the wetland ponds of Turnbull National Wildlife Refuge (TNWR) from April to June 2012, including the invasive European ear snail (Radix auricularia) which was found in four lakes it was not previously known to inhabit. A dominant snail genus was found for each lake, with Middle Pines Lake being dominated by Radix auricularia. Conductivity was the only abiotic factor studied that positively correlated with genera richness (p = 0.035).