Population growth of threatened Gulf Sturgeon may be limited by the frequency of adult episodic mortality events

Objective

We identified spatial and temporal variation in population trends for Gulf Sturgeon Acipenser desotoi (previously known as Acipenser oxyrinchus desotoi) across the species’ range to inform recovery strategies. We also assessed whether adult survival or recruitment more strongly influences population change.

Methods

We analyzed adult Gulf Sturgeon capture–recapture data from 1990 to 2022 across seven Gulf of Mexico river systems. Using temporal symmetry models and fixed estimates of adult survival from a companion study, we estimated seniority probability (γ_{i + 1}), capture probability (p), recruitment (f), and population growth rate (λ) for adult fish. Models were compared using Akaike information criterion adjusted for small sample sizes, and parameter estimates were derived at both river-specific and rangewide scales.

Results

Adult survival (φ) was the primary driver of λ across the species’ range, with γ consistently >0.5 in most rivers and time periods. While rangewide λ suggested stable or slightly increasing adult populations, river-level trends varied. Recent declines in λ and f were observed in the Escambia, Apalachicola, and Suwannee rivers—systems affected by red tide, hurricanes, or oil exposure following the Deepwater Horizon spill. Capture probabilities remained low across rivers and time periods.

Conclusions

Long-term recovery of Gulf Sturgeon is likely more sensitive to adult survival than recruitment to the adult population. Population trajectories differ across rivers and may reflect both demographic changes and inconsistencies in monitoring. Restoring consistent, standardized adult monitoring in select rivers will improve the ability to detect meaningful trends and guide conservation efforts focused on minimizing adult mortality.