Graduation Date

Spring 2024

Document Type



Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Andrew Kinziger

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Eric Bjorkstedt

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Andre Buchheister

Third Committee Member Affiliation

HSU Faculty or Staff


eDNA, Environmental DNA, Tracer, Coho salmon, Steelhead, Streams

Subject Categories



This study was motivated by the need to develop a noninvasive and highly sensitive monitoring tool for determining local occupancy of an endangered aquatic species To make inference into the occupancy of fishes within small stream sites, we developed a method to determine whether environmental DNA (eDNA) concentrations from a target species were elevated relative to a tracer, formulated to mimic eDNA and introduced at a single location. We examined patterns in the observed distribution of the tracer to account for the effects of site-specific transport processes and sampling on distributions of naturally occurring eDNA at small spatial scales (400 meters). Concentrations of two tracers, introduced at high and low concentrations, and eDNA from two target species, coho salmon (Oncorhynchus kisutch) and steelhead (Oncorhynchus mykiss), were simultaneously surveyed in eight study sites across a range of spatial scales (100-400 m). Target species were observed in all study sites during snorkel surveys, thus the expectation was detection of both species, and non-detection would indicate situations where this method required refinement. In total, 128 occupancy assessments were conducted across all study sites, spatial scales, tracers and targets. In 41.4% of assessments, the ratio of target eDNA to tracer significantly increased, providing evidence for additional sources of target eDNA in the study sites (target presence). Using a higher concentration tracer resulted in an increased number of eDNA detections for both targets (51.6%), compared to the low concentration tracer (31.2%), due in part to the broader range over which the higher concentration tracer could be detected. Spatial scale was identified as a crucial factor for species detection, with higher detection rates (63-88%) in assessments conducted on samples separated by 300-400 m, than for samples separated by 100-200 m (25-38%). This study presents a novel approach employing an eDNA tracer to enable species detection in a non-invasive manner at small spatial scales, emphasizing the utility of using a tracer to account for site-specific transport processes. The approach implemented herein was effective with high concentration tracers and at larger spatial scales, but before the approach could be effectively implemented for conservation and management a more diverse set of environmental factors and occupancy scenarios should be explored to evaluate false positive and false negative detection rates.

Citation Style

Transactions of the American Fisheries Society


Thesis/Project Location


To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.