Wagner et al. Simultaneously decontaminating angling gear for New Zealand Mudsnails (<i>Potamopyrgus antipodarum</i>) and Didymo (<i>Didymosphenia geminata</i>): a comparison of two chemical approaches. Data and R code

<b><i>Objective: </i></b>Successful invasion of AIS hinges on effective dispersal which is often greatly facilitated by human activities. A common dispersal mechanism is “hitchhiking’” on aquatic recreational gear and equipment including fishing boats and waders. Two recent co-occurring AIS in the rivers within the Laurentian Great Lakes region are New Zealand mudsnails (NZMS; <i>Potamopyrgus antipodarum</i>) and the algae Didymo (<i>Didymosphenia geminata</i>). Here, we developed and assessed an angling gear chemical decontamination method for NZMS and Didymo.<b><i>Methods:</i></b> Using a fully crossed experimental design, we tested the effectiveness of two household cleaning products (Dawn® dish detergent and the cleaning product Formula 409®) as a decontamination method against NZMS and Didymo. Briefly, we compared the survival and photosynthetic rates of NZMS and Didymo, respectively, when exposed to dish detergent, Formula 409, and a deionized water control to<i> </i>two application techniques (soaking and spraying), and application duration (10- and 20-minutes). NZMS survivorship was assessed over 96 h. Periphyton dominated by Didymo was removed from rocks and oxygen concentrations monitored following a closed chamber photosynthetic assay. Both NZMS survivorship and Didymo photosynthetic rates were assessed with a three-way analysis of variance.<b><i>Result</i></b>: Mean survivorship for NZMS was the greatest for NZMS receiving control water and dish detergent, then Formula 409. Regardless of duration (10- or 20-minute) survivorship of 0% was observed after soaking with Formula 409, while spraying resulted in a survivorship was more variable. Photosynthetic rates of Didymo-dominated periphyton depended on the chemical treatment and application. Significantly lower photosynthetic rates were observed in Didymo that was exposed to dish detergent (5.66 x 10^-5 mg/L/h/mg) and Formula 409 (-0.0003 mg/L/h/mg) compared to the water control (0.003 mg/L/h/mg).<b><i>Conclusion:</i></b> Dish detergent, while effective as a decontaminant for Didymo, is not effective for NZMS. Soaking angling gear in Formula 409 is an effective decontaminant for Didymo and NZMS; however, soaking wading gear is unlikely to be consistently used by wading anglers. Therefore, thorough spraying with Formula 409 is likely to be the more implemented and practical method for minimizing spread of these two invasive species.