In this study, scenario planning was used to explore uncertainty in the future of the Indian Ocean tuna purse seine fishery, focussing attention on the behaviour of fishers. The aim was to stimulate thinking on how the key social, economic and environmental conditions that influence fisher behaviour, which are difficult to accurately forecast, may change in the future, and how these changes might affect the dynamics of fishing effort. A number of key aspects of fishing behaviour suggested in the scenarios as important considerations for policymakers were identified, and the current state of research on these behaviours was briefly reviewed to recommend avenues for future research.