Temporal Variability in Growth Rates of White Sturgeon (Acipenser transmontanus) from the Lower Columbia River: Implications for Abundance Estimation and Fishery Management

Three subpopulations of white sturgeon (Acipenser transmontanus) inhabit the impounded reaches of the Lower Columbia River between Bonneville Dam and McNary Dam. The extensive use of PIT-tags, combined with a long-term mark-recapture program, has allowed the estimation of key population parameters for each impounded subpopulation. These population parameters are incorporated into models used to estimate future abundance and determine appropriate harvest quotas. Recent analysis of long-term growth data has identified a high degree of temporal (annual) variability in growth rates of white sturgeon from the region. For certain size classes of white sturgeon, annual growth rates appear to cycle between periods of rapid growth and periods of slow growth, and vary by as much 300-700% in as little as 4-5 years. This degree of variability has confounded near-term (3-5 year) abundance projections modeled using long-term average growth rates. By incorporating the observed variability in growth rates into the predictive models, resource managers are better able to project the near-term abundance of legal-size white sturgeon and therefore make more informed decisions regarding harvest quotas.