Lower Missouri River Pallid and Shovelnose Sturgeon Population Viability Models with Hierarchical Partitioned Uncertainty

We conducted population viability analyses (PVA) with hierarchical stochasticity for the Pallid Sturgeon (Scaphirhynchus albus) and Shovelnose Sturgeon (S. platorynchus) in the Lower Missouri River. The models apply different components of uncertainty in life history parameters (e.g., survival rates or length-at-age) at different levels in the model: uncertainty about the value of a parameter itself was applied at the iteration level, uncertainty caused by random environmental fluctuations over time was applied at the time-step level, and uncertainty caused by differences between individuals was applied within each time-step. In both species, population dynamics were most sensitive to age-specific survival rates and the number of times an individual could spawn in its lifetime. The partitioning of variance into parameter and temporal components had a strong influence on the importance of individual parameters, uncertainties about predicted population dynamics, and quasiextinction risk. The updated parameter values and inclusion of hierarchical, partitioned variance in our model predicted a greater risk of quasiextinction than previous PVA of these species. Our analyses inform research needs for these species and suggest that the moratorium on commercial fishing of Shovelnose Sturgeon in the Lower Missouri River has probably benefited both Shovelnose and Pallid Sturgeon populations.