The blue mussel is important both ecologically, as a basal species on the food chain and economically, providing the USA with a $7mil harvest each year. For 50 years the range of the blue mussel has been contracting on the central east coast. Preliminary surveys suggest that its numbers may also be declining in the Gulf of Maine (GOM). Blue mussel declines may be due to factors such as climate change, increased storm disturbances, and species invasions. This project seeks to determine population trajectories of blue mussels in the GOM by characterizing abundance, population age structure, reproductive output, and dispersal patterns.This work will allow us to assess the scope of current population declines ñ and identify sources that drive population replenishment ñ throughout the GOM.