The randomised response technique: A valuable approach to monitor pathways of aquatic biological invasions

Anglers can be significant vectors for non-native species (NNS) in freshwater ecosystems, and monitoring their behaviour can be a useful way to counteract biological invasions. However, anglers may be unwilling to reveal their real behaviour in conventional surveys. In this study, the Randomised Response Technique (RRT) and the Bean Method (BM) survey technique were compared using direct questions to obtain frequency estimates of four angler behaviours that may affect NNS management in freshwater ecosystems: angling without a license, release of macroinvertebrates in the environment, use of fish bait and unauthorised fish restocking. Higher estimates were obtained from responses to RRT than BM questions, and BM provided contradictory results. Use of the RRT is recommended in those human dimension studies that explore angler behaviour as a vector for aquatic invasions.