Status of the Shortnose Sturgeon Population in the Savannah River, Georgia

The federally endangered Shortnose Sturgeon Acipenser brevirostrum was once abundant in all major coastal river systems from the Saint John River, Canada, to the St. Johns River, Florida. During much of the 20th century, however, populations suffered major declines throughout their range from the combined effects of overfishing, pollution, and habitat loss. Although the species was a charter member of the Endangered Species Act, quantified population assessments are still lacking for many river systems throughout their range. Because river-specific assessments are critical for evaluating species recovery, the objective of this study was to quantify abundance and annual recruitment of Shortnose Sturgeon occupying the Savannah River, Georgia. Anchored gill nets and trammel nets fished during slack tides were used to sample juvenile and adult Shortnose Sturgeon in their summer holding areas during 2013-2015. Huggins closed-capture models in RMark were used to derive abundance estimates for each demographic group. The best models estimated that the Savannah River contained 81 (95% CI = 27-264) age-1 juveniles in 2013, 270 (162-468) in 2014, and 245 (104-691) in 2015. The models also estimated the river to contain 486 (198-1,273) age-2+ juveniles in 2013, 123 (69-235) in 2014, and 187 (81-526) in 2015. Similarly, the adult population was estimated to be 1,865 (784-4,694) individuals in 2013, 1,564 (1,005-2,513) in 2014, and 940 (535-1,753) in 2015. The results of this study provide the first population estimates available for Shortnose Sturgeon in the Savannah River. Additionally, the results suggest that the Savannah River likely contains the second largest population of Shortnose Sturgeon in Georgia. Future studies are needed in the Savannah River and other South Atlantic river systems to better evaluate Shortnose Sturgeon recovery status and the effects of river-specific anthropogenic modifications.