UW Aquatic & Fishery Sciences Quantitative Seminar

Kevin See

Quantitative Consultants, Inc.

Estimating Salmon Escapement across the Snake River basin: a novel approach using PIT tags

Abstract

Estimates of salmonid adult escapement are crucial to evaluating the status of threatened populations, the success of recovery programs and the productivity of populations. In the Columbia Basin, these estimates are often made using redd counts or mark-recapture models from weir data. Redd counts have (potentially) unknown observation error, and weirs can only be placed in certain locations. Through a tagging program at Lower Granite dam, and the extensive array of instream PIT tag detectors across the Snake River basin, we have developed a hierarchical patch-occupancy model that estimates the probability of fish moving past each detection point, as well as the probability of detection at each site and can then be used to estimate escapement at a variety of spatial scales across the entire basin. In this talk, I will explain how the model works and show comparisons with some independent estimates. However, the trapping rate at Lower Granite Dam is variable over time, violating at least one of this model's assumptions. One potential solution for this violation will be presented.