Philip E. Hulme¹, Sam Beaumont², Paul Champion³ and Daniel Clements³

¹Bio-Protection Research Centre, Lincoln University, Canterbury, New Zealand
²Ministry of Primary Industries, Wellington, New Zealand
³National Institute of Water and Atmospheric Research (NIWA), Hamilton, New Zealand

e-mail: philip.hulme@lincoln.ac.nz

Recreational users of freshwaters (e.g. fishers, boat users etc.) are recognized as leading vectors by which alien plants are spread among lakes. Many countries expend considerable financial resources making lake users aware of the role they play in spreading and the actions they can take to reduce these risks. To date no study has integrated information on the associations between awareness, mitigation and residual risk of different lake users, that might provide insights into more effective management of this introduction pathway. Using data from 1351 interviews of lake users across New Zealand to capture details of more than 1700 lake visits, we present the first comprehensive analysis of this pathway. Interviews were undertaken face-to-face using a standardized questionnaire delivered on a mobile app platform. The questionnaire captured data on the main activity, location of residence, visit frequency, other lakes visited in the last fortnight, awareness of alien freshwater species, and any actions they might take to prevent their spread.

The dominant lake users were water-skiers (27%), swimmers (21%) boat fishers (18%), jetskiers (10%) kayakers (7%) and lakeside fishers (5%) with other users including jetboater, sailors and hikers, less frequent. Awareness of alien plant species was high overall (78%) but with marked variation among user groups. While almost all jetboaters knew the name of at least one alien plant species, this was true for only half of all swimmers. The freshwater diatom, didymo (Didymosphenia geminata), which was subject to a major awareness raising campaign over the last decade, was the most widely known alien species. But this knowledge did not transfer to most alien freshwater plants species. In general, awareness was higher in users who had been directly affected by alien plants, particularly those whose equipment (fishers) or boat engines (jetboaters) were fouled causing negative associations. As a result, it was these users who were most likely to take mitigating actions such as cleaning and/or drying their equipment to prevent further spread. Nevertheless, those most impacted travelled the furthest from home to visit lakes (up to 150km) and visited more lakes within a season. Users who had been negatively impacted by alien freshwater plants generally visited lakes with lower levels of weed invasion than unaffected users. To derive an overall assessment of the risk posed by different users, data on distances travelled, likelihood of visiting invaded lakes, willingness to take action to prevent spread and the relative abundance of users were integrated. As a result, this study highlights that the highest risk to lakes is posed by powerboat users (water-skiers and boat fishers), while sailboats represent a lower risk. Water-skiers have not been a major target for awareness raising and their risk may have been underestimated historically. This study recommends that awareness raising should better target boat users, particularly water-skiers, focusing on the impacts upon their leisure activity rather than biodiversity.