Movement Patterns of Shortnose Sturgeon Acipenser brevirostrum in the Savannah River, GA

The Savannah River is home to one of the 16 known populations of shortnose sturgeon (Acipenser brevirostrum) remaining. Damming, alterations of river channels, changes in flows, harbor deepening, and overfishing are all human induced factors that have contributed to the decline of Savannah River shortnose sturgeon. A partnership of agencies and organizations are working together to monitor shortnose sturgeon movement in the Savannah River to better assess their critical habitat use.  In 2006 through 2009, a total of 34 adult shortnose sturgeon were tagged with acoustic transmitters and tracked by an array of receivers deployed throughout the river system. Data from receivers were downloaded into VUE software (Vemco) and Excel for analyses of fish distribution and movement patterns. A total of 573,461 detections were used for analysis. Individual sturgeon were tracked from 1 to 874 (mean = 305 ± 69 days). The Savannah River, at the estuary, branches into three major channels called Front, Middle, and Back rivers. Fish use was higher in the Front River compared to the Middle and Back rivers combined as indicated by both number of detections and movement patterns. Most of the fish traveled throughout the Front and Middle rivers but not the Back River. This is the first documented evidence that sturgeon moved between rivers using human-made channels. These artificial channels play an important role in how shortnose sturgeon are able to access critical estuarine foraging habitat or refugia from summertime hypoxic conditions. Proposed deepening of the Savannah River harbor may limit shortnose sturgeon movement since alterations of these channels are proposed. Results from this effort are helping to inform resource managers about potential habitat requirements for the shortnose sturgeon and are providing best-available information for decision making regarding harbor deepening. Findings of this study have been used to secure support and multi-agency cooperation for a longer term study with more receivers to further refine movement patterns.