https://www.selleckchem.com/products/vx-561.html Communities throughout the globe are increasingly being given the responsibility of resource management, making it necessary to understand the factors that lead to success in community-based management (CBM). Here, we assessed whether and how institutional design principles affect the ecological outcomes of CBM schemes for Arapaima sp., an important common-pool fishery resource of the Amazon Basin. We quantified the degree of presence of Ostrom's (Science 325419-422, 1990) institutional design principles in 83 communities using a systematic survey, and quantitatively linked the design principles to a measure of ecological outcome (arapaima density) in a subset of 39 communities to assess their influence. To understand regional patterns of institutional capacity for CBM, we evaluated the degree of presence of each principle in all 83 communities. The principle scores were positively related to arapaima density in the 39 CBM schemes, explaining about half of the variation. Design principles related to defined boundaries and graduated sanctions exerted the strongest influence on the capacity of CBM to increase arapaima density. The degree to which most principles were present in all 83 communities was generally low, however, with the two most influential principles (defined boundaries and graduated sanctions) being the least present of all. Although the roles of the other principles (management rules, conflict resolution, collective action, and monitoring systems) are probably important, our results indicate that efforts aimed at strengthening the presence of defined boundaries and graduated sanctions in communities hold promise to improve the effectiveness of arapaima CBM regionally.East African ecosystems have been shaped by long-term socio-ecological-environmental interactions. Although much previous work on human-environment interrelationships have emphasised the negative impacts of human interventions, a growing bod