Abundance and Recruitment of Juvenile Atlantic Sturgeon in the Altamaha River, Georgia

Juvenile Atlantic sturgeon Acipenser oxyrinchus remain in natal rivers for several years prior to out-migrating to marine environments during later portions of their life history. Data regarding river-resident juvenile population dynamics are unknown. During the summers of 2004-2007, we performed mark-recapture of juvenile Atlantic sturgeon in the Altamaha River to assess age-specific abundance, apparent survival, per capita recruitment, and factors influencing recruitment. Estimates indicated that juvenile abundance ranged from 1,072 to 2,033 individuals, and age-1 and age-2 individuals comprised greater than 87% of the juvenile population, while age-3 or older individuals constituted less than 13% of the population. Estimates of apparent survival and per capita recruitment from Pradel models indicated that the juvenile population experienced high annual turnover: apparent survival rates were low (<33%), and per capita recruitment was high (0.82-1.38). Fall discharge, which had a positive relationship with recruitment, was the only factor assessed that significantly explained time variation in per capita recruitment. The findings of this study suggest that juvenile populations at the southern extreme of the Atlantic sturgeon's range may remain in natal rivers for less time than northern counterparts. This is further evidence of life history differences between northern and southern populations of Atlantic sturgeon. Potential findings of density dependence could have major implications for both population recovery and management of this species.