Hatchery-origin pallid sturgeon (Scaphirhynchus albus) have been stocked into the upper Missouri River above Fort Peck Dam since the late 1990s in response to a lack of natural recruitment. Understanding when the hatchery-origin fish within the population reaches sexual maturity is critical to understanding the effectiveness of the program in recovering this federally endangered species. Using combined historical and contemporary data (n=752; 2011-2024), we described sex-specific relationships between age and size at first maturity and spawning periodicity and evaluated false maturation rates in female pallid sturgeon. Males are reaching sexual maturity at a smaller size and younger age than females. Males are physiologically capable of annual spawning, but not all males spawned every year. Females are physiologically capable of spawning every two years, but the spawning periodicity ranged from two to five years once sexual maturity was attained. False maturation occurred during the first reproductive cycle as females initiated but failed to complete vitellogenesis, and mass follicular atresia was found to occur in some subsequent cycles. The rate of false maturation was compared to the rate of mass follicular atresia occurring in females that had spawned previously. Understanding fish reproductive biology is essential for successful management and conservation of this species.

reproduction,spawning periodicity,pallid sturgeon,age at first maturity,size at first maturity