Stat Colloquium (Virtual): Dr. Meenu Mahankumar

Title: A Time-Integrated Migration and Survival Model for Estimating Survival and Migration of Fish Populations

Abstract: The survival and migration dynamics of juvenile salmonids in hydroelectric systems are governed by a complex interplay of environmental conditions and dam operations. Statistical inference in this setting is often complicated by imperfect detection and uncertainty in individual passage times. We address these challenges using a Time-Integrated Migration and Survival (TIMS) model to analyze yearling Chinook salmon (Oncorhynchus tshawytscha) and steelhead (O. mykiss) at Little Goose Dam (LGS) in the Columbia River hydrosystem.

TIMS is a hierarchical multi-state mark-recapture framework that embeds a migration submodel for travel time between detection arrays, enabling survival and migration rates to be modeled as explicit functions of time-varying covariates, while accounting for unobserved passage times. Using acoustic telemetry data, we evaluate individual-level effects (e.g., fish length) and time-varying factors (e.g., water velocity, spill discharge, temperature, etc.). Analyses are conducted across multiple reaches spanning upstream of LGS, through the LGS Dam, and downstream to Lower Monumental and McNary Dams. This framework offers a robust method for estimating survival and migration rates under dynamic conditions, thereby enhancing inference on how operational factors impact biological performance in regulated river systems.