In 2015-2016, Florida Bay, within Everglades National Park (ENP), experienced a significant seagrass die-off. The park has estimated over 16,000 hectares of the seagrass beds have been affected by the die-off (NPS fact sheet). In tropical estuaries seagrass beds are ecologically and economically critical resources. They are especially important as feeding and foraging areas for sportfish including Albula vulpes (bone fish), Megalops atlanticus (tarpon) and Trachinotus falcatus (permit). The sportfish supported by Florida Bay’s seagrass beds are all highly sought after by anglers, with the local fishing industry contributing more than $6 billion in revenue to the state of Florida each year (Johns et al., 2001). Worldwide seagrass beds are disappearing due to stress from land-use changes, improper anchoring and mooring practices, boat propeller scarring, global climate change, disease, invasive species and algal blooms. This project examined the extent of Florida Bay’s seagrass die-off using two complementary methods. First, we measured seagrass densities at 61 sample locations in Florida Bay basins during fieldwork campaigns in the summers of 2016 and 2017. Nearest neighbor analysis conducted in a geographic information system (GIS) was used to extrapolate these in situ observations to larger basin-wide spatial scales. Second, we mapped and calculated the perceived extent of the die-off using citizen science, consulting local knowledge keepers through the Key Largo Fishing Guides Association and Florida Keys Fishing Guide Association. These two methods allow us to gain a better understanding of the impacts of the die-off, and develop data sets that will inform future assessments of change and recovery in these important habitats.