Abundance of Juvenile Atlantic Sturgeon in the Ogeechee River, Georgia

The Atlantic sturgeon (Acipenser oxyrinchus) was once widely abundant, but populations declined because of over-harvest and habitat degradation. The commercial fishery for Atlantic sturgeon was closed in the United States in 1996. Population status and recovery of the species is a primary management need. River-resident juvenile sturgeon provide an opportunity to conduct mark-recapture studies and estimate abundance. The goal of this study was to estimate abundance of juvenile Atlantic sturgeon in the Ogeechee River, Georgia. Mark-recapture data were collected June-August of 2007. Sturgeon were captured using anchored gill and trammel nets set perpendicular to the flow during slack tides. A 0.5- to 1.0-cm section of the leading edge of the pectoral spine was removed from a random sub-sample of 18 juvenile sturgeon for subsequent age determination. Data were analyzed in Program MARK using a Huggins closed capture design model. A set of candidate models were constructed using the covariates of average weekly water temperature, weekly number of nets, and weekly time of net sets in hours. The relative likelihood of each model was evaluated by calculating AICc. The most plausible model included water temperature and net hours as covariates. The abundance of juvenile Atlantic sturgeon in the Ogeechee River was estimated to be 450 (203-1125) in 2007. The results of this study provide the first estimates of juvenile Atlantic sturgeon abundance in a population at the southern extent of their range. Studies in other river systems can use our methods to estimate juvenile Atlantic sturgeon abundance by river system. Post-harvest population recovery of Atlantic sturgeon should be monitored to evaluate the effectiveness of the closure of the fishery. Annual monitoring of age-1 abundance may indicate trends in Atlantic sturgeon recruitment.

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