Biosecurity and Preventing the Spread of Freshwater Invasive Species

Invasive alien species (IAS) are of global concern due to a range of negative impacts. Biosecurity is key to reducing the risk of accidental IAS spread. This thesis explores biosecurity effectiveness and the risk of freshwater IAS spread, focusing on the vector-stowaway pathway. Chapters 2-5 assess the effectiveness of biosecurity practices to remove/kill freshwater IAS attached to vectors such as watercraft, equipment and clothing. Used by stakeholders to clean vectors, disinfectants and chlorine solutions are licenced for use against microbes. However, their effectiveness against IAS is little tested. Chapter 2 demonstrates immersion (1% for 2 minutes) and spray treatments (5 sprays of 2%) of disinfectants to be effective in inducing complete Dikerogammarus villous mortality. Immersion in chlorine solutions had varying effectiveness (Chapter 3). Short immersion durations of 10 minutes in 500mgL-1 resulted in complete D. villosus mortality, as did spray applications. Longer treatments were required to achieve high Dreissena polymorpha (4000mgL-1 for 8 hours) and Hydrocotyle ranunculoides (2000mgL-1 for 6 hours) mortality. However, low mortality of Crassula helmsii was seen in all treatments. In Chapter 4, disinfectant and chlorine treatments identified as effective against D. villosus were found to be effective against Dikerogammarus haemobaphes. Hot water spray is used to clean large vectors, but there are knowledge gaps in its effectiveness against IAS (Chapter 5). In field conditions, 90oC spray applied for 15 seconds from 10cm resulted in complete D. villosus and D. polymorpha mortality. Fragmentation and complete mortality was seen in H. ranunculoides following cold and hot water spray. However, high C. helmsii survival was observed. Chapter 6 assesses the risk of IAS spread associated with paddlesport and motivation for and barriers to biosecurity. The survey revealed frequent use of equipment/clothing in different water catchments and abroad, however paddlers report high levels of engagement with biosecurity practices. Chapter 7 includes recommendations for CASE partners and stakeholders to improve biosecurity guidance and uptake.