Annual Run Size and Genetic Characteristics of Atlantic Sturgeon in the Altamaha River, Georgia

Abstract

Although the Altamaha River, Georgia, once supported one of the largest fisheries for Atlantic sturgeon Acipenser oxyrinchus in U.S. waters, the fishery was closed in 1997 because of severe overfishing. Since then, no studies have been conducted and population trends have remained unknown. The objective of this study was to estimate annual run size and age structure of the spring spawning migration and to determine genetic relatedness between this population and other Georgia populations. In spring of 2004 and 2005, we sampled the annual spawning run of Atlantic sturgeon in the lower 30 km of the Altamaha River using large‐mesh gill nets. Captured fish were marked with passive integrated transponder tags and released to facilitate a run estimate using a simple Schnabel mark‐recapture estimator. Over the 2 years of the study, we captured 213 individuals, yielding mark‐recapture run estimates of 324 (95% confidence interval [CI] = 143‐667) in 2004 and 386 (95% CI = 216‐787) in 2005. Catch curve analysis yielded annual mortality rates of 17.3% in 2004 and 21.3% in 2005. Genetic analysis showed that the Altamaha River population is distinct from neighboring populations in the Ogeechee and Savannah rivers. The results of this study suggest that after 10 years of federal protection, the Altamaha River population of Atlantic sturgeon appears to be in the early stages of recovery; however, the genetic diversity of the population is surprisingly low. Future studies are needed to monitor population dynamics and genetic structure of the stock to ensure complete recovery.