Evaluating Population Recovery Characteristics and Potential Recovery Actions for a Long‐Lived Protected Species: A Case History of Gulf Sturgeon in the Apalachicola River

Abstract

AbstractIn the U.S. Gulf of Mexico, Gulf Sturgeon Acipenser oxyrinchus desotoi supported an intense and short‐lived commercial fishery in the early twentieth century. Thereafter, it persisted at very low levels until the fishery was closed by individual U.S. states in the Gulf of Mexico region in the mid‐1980s. Despite the closure of the fishery, the stock has not recovered and there have been threats to population recovery including the potential effects of the Deepwater Horizon oil spill, storm events, and harmful algal blooms. We developed an age‐structured population model for Gulf Sturgeon to examine their population recovery characteristics. We paired this model with simple population reference points to assess the factors that influence the population recovery rate and strategies that resource managers could adopt to promote the recovery of the species. We used the Gulf Sturgeon population in the Apalachicola River as a case history and the date of 2023 that has been identified in Gulf Sturgeon Recovery Plan (GSRP) as the point at which to evaluate recovery, and under current management we predict that (1) age‐4+ Gulf Sturgeon (fish 4 years of age and older) will be approaching 50% of current estimated carrying capacity; (2) the dynamic spawning potential ratio is likely >0.3, suggesting a low chance of recruitment overfishing; (3) the population age structure is likely slowly recovering; (4) the recovery of the Gulf Sturgeon population is sensitive to increases in total mortality; and (5) the estimated values for exploitation rate (UMSY) and biomass at maximum sustainable yield (BMSY) are about 0.058 and 1,859 kg (or <200 age‐4+ fish per year [age‐4 and older fish]), respectively. Our results demonstrate the relative efficacy and influence of various recovery efforts and threats, respectively, and demonstrate that “recovery” is much different when it is based on historic versus currently available habitat. These model results provide reference points for comparing field assessments as part of the planned restoration efforts and upcoming population status reviews for Gulf Sturgeon that are funded as part of the Natural Resource Damage Assessment following the Deepwater Horizon oil spill.