The sea lamprey is an invasive species in the Great Lakes for which trapping might provide an important control option if trapping efficiency could be improved. In Chapter 1, I examined the behavioural basis for low trapping efficiency by developing a conceptual framework consisting of several states, and quantifying the behaviour of individuals as they move through these states. My results suggest that trapping efficiency is low due to low probabilities of encounter and entrance and that the trapping process is influenced by sea lamprey class and release date but not body size or trap location. In Chapter 2, I quantified movement paths of sea lamprey approaching and departing trap locations to test whether they used the same route and whether they aggregated spatially. My results suggest that sea lamprey do not all use the same route, but some are much more likely to visit some areas than others.