The diverse impacts of shipping activities on the marine environment are now recognized and increasingly documented, particularly with regards to marine mammals. In recent years, governments have committed to enhancing the protection of the marine environment, notably through the creation of marine protected areas. The Automatic Identification System (AIS), originally introduced for maritime safety and traffic control, has become an essential tool for the management of shipping activities for the conservation of marine environments. The present paper uses the Saguenay–St. Lawrence Marine Park (Québec, Canada), recognized for its high diversity of marine mammals and intensive traffic, to highlight the different potential uses of AIS data in the management of a marine protected area. Examples presented include describing baseline vessel use of a maritime area, assessing and modelling the environmental impacts of the shipping activities, and monitoring compliance to management measures. The different benefits of using AIS data in a conservation context are illustrated, and their limitations are outlined.