Small-scale fisheries collectively have a large ecological footprint and are key sources of food security, especially in developing countries. Many of the data-intensive approaches to fishery management are infeasible in these fisheries, but a strategy that has emerged to overcome these challenges is the establishment of territorial user rights for fisheries (TURFs). In this approach, exclusive fishing zones are established for groups of stakeholders, which eliminates the race to fish with other groups. A key challenge, however, is setting the size of TURFs-too large and the number of stakeholders sharing them impedes collective action, and too small and the movement of target fish species in and out of the TURFs effectively removes the community's exclusive access. We assessed the size of 137 TURFs from across the globe relative to this design challenge by applying theoretical models that predict their performance. We estimated that roughly two-thirds of these TURFs were sized ideally to overcome the challenges posed by resource movement and fisher group size. However, for most of the remaining TURFs, all possible sizes were either too small to overcome the resource-movement challenge or too large to overcome the collective action challenge. Our results suggest these fisheries, which target mobile species in densely populated regions, may need additional interventions to be successful.
