Invaders in hot water: a simple decontamination method to prevent the accidental spread of aquatic invasive non-native species

Watersports equipment can act as a vector for the introduction and spread of invasive non native species (INNS) in freshwater environments. To support advice given to recreational water users under the UK Government's <i>Check Clean Dry</i> biosecurity campaign and ensure its effectiveness at killing a range of aquatic INNS, we conducted a survival experiment on seven INNS which pose a high risk to UK freshwaters. The efficacy of exposure to hot water (45 °C, 15 min) was tested as a method by which waters users could 'clean' their equipment and was compared to drying and a control group (no treatment). Hot water had caused 99 % mortality across all species 1 h after treatment and was more effective than drying at all time points (1 h: χ² = 117.24, <i>p</i> < 0.001; 1 day χ² = 95.68, <i>p</i> < 0.001; 8 days χ² = 12.16, <i>p</i> < 0.001 and 16 days χ² = 7.58, <i>p</i> < 0.001). Drying caused significantly higher mortality than the control (no action) from day 4 (χ² = 8.49, <i>p</i> < 0.01) onwards. In the absence of hot water or drying, 6/7 of these species survived for 16 days, highlighting the importance of good biosecurity practice to reduce the risk of accidental spread. In an additional experiment the minimum lethal temperature and exposure time in hot water to cause 100 % mortality in American signal crayfish (<i>Pacifastacus leniusculus</i>), was determined to be 5 min at 40 °C. Hot water provides a simple, rapid and effective method to clean equipment. We recommend that it is advocated in future biosecurity awareness campaigns.