The hilsa is a critically important species for smallscale fishing communities in Myanmar’s Ayeyarwady Delta and Rakhine State. Yet current fishing regulations are inadequate and exploitation rates are well beyond sustainable levels. This study analyses key parameters underlying hilsa biology, comparing them across different ecological zones of the hilsa’s range in Myanmar and across time. It provides evidence of major spawning activity between July and September in the freshwater zone, particularly in September. We recommend that policymakers restrict access to fishing in freshwater areas at least during the month of September; promote and enforce measures to protect juvenile hilsa; establish marine protected areas to conserve spawning stock biomass; and ensure effective, adaptive fisheries management throughout migratory routes.