Atlantic Sturgeon Movements and Habitat Use in the Penobscot River, with Implications of Dam Removal

Historically, coastal rivers along the Atlantic coast supported large populations of Atlantic sturgeon (Acipenser oxyrinchus), but overharvest, habitat loss, and habitat degradation have decimated populations. Since 2006, 181 Atlantic sturgeon have been captured, 43 of which were tagged with acoustic transmitters, and monitored in the Penobscot River, Maine. Over seven years, three major movement patterns were observed for Atlantic sturgeon in this system: “summer residents” arrived in spring, stayed all summer and left in fall (n=54 observations), “quick visitors” arrived in spring and left within several days (n=3 observations), and “river and bay users” entered and left the Penobscot several times throughout the summer (n=24 observations). Some individuals repeated movement patterns each year, while some individuals displayed different patterns in different years. The furthest upstream detections were at 40 rkm, but fish spent most of their time between 20-25 rkm, where the substrate is muddy and rich in spionid worms. These observations suggest that this is an important foraging area. Recently, two dams have been removed on the Penobscot River. It remains to be seen if and how movement patterns and habitat use will change now that the entire historic habitat is available.