Status and population trends of shortnose sturgeon (Acipenser brevirostrum) in the Altamaha River, Georgia

Although the shortnose sturgeon was listed as endangered in 1967, most populations remain depressed with few river systems supporting >1000 individuals. Within the southern half of the range, the Altamaha River is believed to support the largest discrete population segment, based on a 2004 estimate of 6,300 total individuals. Although this previous estimate provided the first comprehensive assessment of the Altamaha population, continued recovery is uncertain because long-term studies of shortnose sturgeon are lacking for southern rivers. The objectives of this study were to quantify recent trends in abundance, age structure, and recruitment of shortnose sturgeon in the Altamaha River. From 2004-2009, we used entanglement gear to conduct mark-recapture estimates of the population using the full likelihood closed-capture models in Program MARK. Over the six years of the study, we captured 1449 shortnose sturgeon (54 recaptures) in 854 net sets. Our results show that while adult abundance has remained relatively constant, juvenile recruitment is highly variable, causing dramatic shifts in population structure. Further study is needed to identify key environmental factors affecting annual recruitment in the Altamaha and other southern rivers.