Simultaneously decontaminating angling gear for New Zealand mudsnails <i>Potamopyrgus antipodarum</i> and didymo <i>Didymosphenia geminata</i>: A comparison of two chemical approaches

ABSTRACT Objective Successful invasion of aquatic invasive species (AIS) hinges on effective dispersal, which is often 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 of the Laurentian Great Lakes region are New Zealand mudsnails (NZMS) Potamopyrgus antipodarum and the algae didymo Didymosphenia geminata. Here, we developed and assessed an angling-gear chemical-decontamination method for NZMS and didymo. Methods 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 with two application techniques (soaking and spraying) and application durations (10 and 20 min). Results Mean survivorship for NZMS was the greatest for NZMS receiving control water and dish detergent, then Formula 409. Regardless of duration (10- or 20-min), survivorship of 0% was observed after soaking with Formula 409, while spraying resulted in a survivorship that 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 × 10–5 mg·L–1·h−1·mg−1) and Formula 409 (−0.0003 mg·L–1·h−1·mg−1) compared to the water control (0.003 mg·L–1·h−1·mg−1). Conclusion 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.