We report the results of common-pool resource economic experiments conducted with indigenous communities in the Colombian Amazon. The experiments recreate two contexts: a limited open access with no institutions regulating the fisheries and a nonmonetary external regulation that limits individual extraction when a fisher is found to be overextracting. We find that variables that did not explain behavior under limited open access do so under the regulatory institution. In particular, when the nonmonetary external regulation was introduced, we found a nonlinear significant effect of age on individual harvest. This result implies a negative relationship between age and individual extraction that reaches a peak around age 54. Our results suggest that in our sample, age groups react differently to an institution aimed to manage the fishery and open a discussion regarding the role of older fishers when a new regulation is introduced to manage natural resources. Their role could go beyond the dissemination of traditional knowledge and cultural systems since older fishers could be key actors in disseminating and adapting new institutions.