The Planning for an Environmental Response (PIER) initiative falls under the umbrella of the Government of Canada's Oceans Protection Plan (OPP), whose goal is preserving marine ecosystems vulnerable to increased transportation and the development of the marine industry (https://pm.gc.ca/en/news/backgrounders/2016/11/07/canadas-oceans-protection-plan-preserving-and-restoring-canadas). The PIER was established in response to recommendations made in a 2013 report "A review of Canada's ship-source spill preparedness and response regime " by the Tanker Safety Expert Panel (https://tc.canada.ca/en/marine-transportation/marine-safety/tanker-safety-expert-panel). One of the recommendations calls on Fisheries and Oceans (DFO) to work with Environment and Climate Change Canada (ECCC) to collect and compile information on sensitive species and environments for each Canadian Coast Guard (CCG) response area and make it publicly available. The PIERs’ main mandate is to acquire and update biological sensitivity data under its jurisdiction for preparation and response purposes in the event of an oil spill. With DFO-Science, PIER supports ECCC's National Environmental Emergencies Centre (NEEC) and the CCG in their preparations and responses through the sharing of data on biological sensitivities, the development of response tools and expert advice. In this vein, DFO published an analysis in 2018 that aimed to identify the most vulnerable components of the St. Lawrence in order to prioritize them during data collection if gaps were identified (Desjardins et al. 2018). This exercise highlighted the vulnerability of several biological components and important data gaps, particularly in coastal areas. As a result of this finding, the Quebec region PIEI team embarked on a collaborative project with the Université du Québec à Rimouski (UQAR) to map eelgrass beds, tidal marshes and macroalgal beds. In consultation with other DFO-Science data producers, this team has also created datasets adapted for response purposes, notably regarding bivalves and marine mammals. These layers may be used for oil spill preparedness and response by DFO-Quebec Region's Environmental Incident Coordinator, NEEC and CCG. Several of them, deemed relevant in the first 72 hours following a spill, have been transmitted to the NEEC.