AbstractSmall-scale fisheries (SSFs) are significant for poverty alleviation, but are threatened by over-exploitation and climate change effects such as drastic drops in regrowth rates. How will fishers adapt? To shed light on this, we ran a common-pool resource experiment with SSF fishers in Thailand. Our results show that groups confronted with a potential abrupt drop in the regrowth rate are more likely to form cooperative agreements compared to groups not confronted with such a drop, which theory cannot predict. However, groups that form cooperative agreements do not necessarily manage the resource efficiently; many groups under-exploit. Over-exploitation is driven by individual characteristics, e.g., if individuals can diversify income, and if they are born outside the village. We conclude that more systematic exploration of the role of socio-economic factors, and how these factors interact with ecological conditions facing fishers, are needed. Our work can be seen as one step in this direction.