Ecological indices are a powerful tool to assess ecosystem status. The Cree first nation of James Bay northern Quebec rely on eelgrass (Zostera marina L) locally known as 'Sishkabash' for the coastal ecosystem services. However, eelgrass in James Bay has declined since the 1980s without a clear cause nor a method to quantify its current state. To assess eelgrass health in James Bay, we developed the eelgrass health index (EHI) using underwater video-monitoring observations. The EHI provides an overall health rating of eelgrass meadows using standard eelgrass abundance metrics. It was was calibrated and validated using field data from James Bay and independent monitoring sites in the United States and from expert knowledge. The EHI demonstrates that eelgrass health is impaired across James Bay with only few healthy meadows remaining.
