UW Aquatic & Fishery Sciences Quantitative Seminar

Rebecca Buchanan

UW -- Columbia Basin Research

Using Release-Recapture Methods to Estimate Salmon Survival in a Complex Environment

Abstract

Release-recapture tagging studies have long been used to estimate survival of migrating populations such as Pacific salmon. As resource management needs intensify, both the questions asked about migrating salmonids and the technology used in release-recapture studies have grown more sophisticated. The advent of small acoustic telemetry tags has expanded our ability to track juvenile salmonids as they migrate to the ocean, and has shifted focus from large riverine reaches to smaller reaches through complex environments such as river deltas. The focus on river deltas has introduced a variety of complications, including limitations of a non-linear channel network on study design, multi-directional movement of study fish, and false positive detections resulting from predation by predatory fish that move past one or more detection arrays. Tag failure and questions of spatial scale complicate data interpretation, as well. In this talk, I will give a short introduction to the concepts behind release-recapture studies, and discuss complications encountered in a large, multi-year acoustic-tagging study of juvenile Chinook salmon in the San Joaquin River Delta of California.