Biosecurity measures to reduce secondary spread of the invasive freshwater Asian clam, Corbicula fluminea (Müller, 1774)

Invasive species are currently considered one of the most important threats to global biodiversity. Established invaders are difficult to
eradicate and management requires biosecurity measures to prevent secondary spread. Corbicula fluminea (Müller, 1774; Asian clam) has a
worldwide invasive distribution and, as an ecosystem engineer, can have dramatic impacts on recipient systems, displacing native species
and altering trophic structure. This study tested the efficacy of biosecurity methods for cleansing angling equipment (such as nets and
waders) and other gear used in freshwater that may harbour C. fluminea and contribute to their secondary spread. C. fluminea of varying size
were treated either with Virkon® Aquatic, common household bleach or salt at a variety of concentrations for a range of immersion times.
Virkon® emerged as the most effective of the three treatment types and achieved 93.3% mortality when used at 2% for 5 minutes. With the
bleach trials, there was no significant effect of immersion time on clam mortality, but 10% bleach for 60 minutes induced an average
mortality of 76.7%. Further, maximum mortality in saltwater was only 13.3% with 60 minutes immersion. There was no significant
difference in mortality among clam sizes. Virkon® is, therefore, recommended as the most effective product for treating angling and other
gear that could potentially harbour and spread C. fluminea. We also assessed the effect of ‘drying times’ post-treatment and this was
demonstrated to have no significant effect on clam mortality. Virkon® again gave the highest mortality of the three treatments, with 68.9%
mortality achieved at 2% for 10 minutes. Overall, Virkon® emerges as an effective biosecurity measure, but further research is required to
attain 100% mortality. Bleach may be useful when Virkon® is not available, but salt is relatively ineffective