Risk of invasive species spread by recreational boaters remains high despite widespread adoption of conservation behaviors.

The spread of non-native aquatic species among waterbodies has become a major social, environmental, and economic concern. An important mechanism of this spread is the inadvertent transport of organisms on recreational boats as they are moved among waterbodies. Organisms can survive on the exterior of the boat, the interior, attached to fishing tackle, and can be intentionally moved by boaters. In response, local, state, and federal U.S. agencies have invested in outreach campaigns to educate boaters about the impacts of invasive aquatic species and the ways that boaters can reduce the risk of spread. We surveyed boaters in the U.S. state of Illinois to determine their travel patterns and how frequently they clean different parts of their boats. A majority of boaters reported that they always take recommended actions to clean their boat exterior (72% of respondents), boat interior (78%), and fishing tackle (55%), and only 4% reported that they intentionally move organisms. We used network methods to analyze the movement of recreational boaters and found strong connections among 28 highly visited waterbodies. When we removed the 38% of respondents who Always take recommended actions to reduce risk of species spread by all four mechanisms this network was minimally altered and still contained all 28 waterbodies. This indicates that despite high adoption of conservation behaviors there is a continuing risk of non-native species transport among all waterbodies. This work shows that further action is necessary if the impacts of invasive aquatic species are to be reduced in the future.