Mangrove clam or imbao (Pegophysema philippiana) is an economically important bivalve species that is very common in the vast mangrove forest in the Davao region. This marine mangrove resource is subject to overexploitation and indiscriminate gleaning. Small clams are frequently gleaned in the provinces of Davao Oriental, Davao Occidental, and Davao del Sur negatively impacting the supply of imbao in the market. A size regulation policy was established in which gleaners were prohibited from collecting sexually immature clams (below 4 cm). After several years of implementing size regulation policy, the mangrove clam stock continuously declined. A rotational harvest strategy was introduced. A cyclical closure of the subdivided plots in each province was imposed. After a year of closure, the wild population of mangrove clams increased especially in Davao Oriental and Davao Occidental. While in Davao del Sur no significant enhancement was observed. The policy change to conserve mangrove clam is a vital step in sustaining this species in the region. However, cooperation, awareness, and adherence to the policy being implemented in the province are factors that influence the effectiveness of the policy