Each spring, about 600,000 river herring migrate from the Gulf of Maine to the Mystic River, lakes and ponds to spawn. We used acoustic tagging with the Massachusetts Division of Marine Fisheries to learn about their movement throughout the system and the effect of fish passage structures. This pilot study will inform the Massachusetts Division of Marine Resources with regards to management of spawning populations, as well as identify specific locations for focusing larger river herring monitoring efforts to better understand our annual visitors. The Massachusetts Bays National Estuary Program (MassBays) provided funding in support of this project, with additional support from Woods Hole Research Center Mystic River Watershed Association. Read the spotlight at seagrant.mit.edu now!