Recruitment and survival of juvenile Gulf sturgeon (Acipenser oxyrinchus desotoi) in the Apalachicola River in Florida

The Gulf sturgeon (Acipenser oxyrinchus desotoi) is an anadromous fish found in drainages of the Gulf coast from Louisiana to Florida and is federally listed as threatened under the Endangered Species Act. Estimates of abundance of adult Gulf sturgeon from several studies have been reported, but direct quantification of juvenile abundance has not been attempted-although such information regarding annual recruitment and juvenile population trends is critical. Our objectives were to quantify recruitment of Gulf sturgeon in the Apalachicola River in Florida by estimating age-1 juvenile abundance and to investigate their survival. During May-August in -2013-2018, we used entanglement gear to conduct a mark- -recapture assessment of juvenile Gulf sturgeon. Using Huggins closed population models, we estimated that the Apalachicola River produces 28-210 age-1 juveniles annually (mean: 70 individuals [standard deviation 69.4]). Acoustic telemetry data collected from a subset of age-1 fish indicate that the study area was closed during sampling. We conservatively estimated overwinter survival on the basis of detections and recapture of age-2+ fish acoustically tagged at age 1. Survival varied among years from 33% to 90%. These results indicate that direct estimates of recruitment of Gulf sturgeon to age 1 are feasible, but it is difficult to determine whether this population is recruitment limited without similar data for other populations of Gulf sturgeon.