Demographic Factors and Male Behavioral Plasticity Affect Male and Female Reproduction Success and Temporal Variation in Effective Breeding Number in Lake Sturgeon

Quantifying inter-annual variation in effective adult breeding number (N_b) and relationships between N_b, effective population size (N_e), adult census size (N) and population demographic characteristics are important to predict genetic changes in populations of conservation concern. Such relationships are rarely available for long-lived iteroparous species like lake sturgeon (Acipenser fulvescens). We estimated annual N_b and generational N_e using genotypes from 12 microsatellite loci for lake sturgeon adults (n=796) captured during 8 spawning seasons and offspring (n=3,925) collected during larval dispersal in a closed population over 10 years. Inbreeding and variance N_b  derived using multiple estimators were similar within and among years (inter-annual range of N_b: 41-205). Variance in reproductive success and unequal sex ratios reduced N_b relative to N on average 36.8% and 16.3%, respectively. Inter-annual variation in N_b/N ratios (0.27 - 0.86) resulted from stable N and low standardized variance in reproductive success due to high proportions of adults breeding and the species’ polygamous mating system, despite a 40-fold difference in annual larval production across years (437 – 16,417). Results indicated environmental conditions and features of the species’ reproductive ecology interact to affect demographic parameters and N_b/N. N_e may not be approximated as the product of average annual N_b and generation length (g). Therefore, supplemental breeding programs would be ill advised to divide the targeted N_e into a series of (g) annual target effective numbers (N_b).  Results have important implications for genetic monitoring and conservation planning for lake sturgeon and other species with similar life histories and mating systems.