Ian Jezorek¹, Earl F. Prentice², Patrick J. Connolly³

1. U.S. Geological Survey, 5501A Cook-Underwood Rd., Cook, WA 98605
2. National Marine Fisheries Service - Retired
3. U.S. Geological Survey - Retired

In 2001 U.S. Geological Survey and National Marine Fisheries Service staff installed an instream PIT-tag detection site in Rattlesnake Creek, WA, a tributary of the White Salmon River. Though PIT tagging had been in practice for years and dams in the Columbia River system had some detection capability, the concept of instream detection was new to the Columbia River basin. The Rattlesnake Creek site was an experiment to test efficacy of instream detection of rainbow trout Oncorhynchus mykiss tagged with full-duplex PIT tags. Many challenges were faced, including transceiver performance and noise issues as well as antenna considerations including adequate coverage, orientation, and anchoring. Initial operation began with two antennas, each paired with a stand-alone transceiver. As the site evolved over the six years of operation, improvements were made in transceiver technology that increased read range, increased the number of antennas operable to six, and improved communication and data handling options. Additionally, lessons were learned, sometimes painfully, about antenna and cable deployment and anchoring techniques. Despite the challenges, the site worked well and provided much data on O. mykiss movement between Rattlesnake Creek and the White Salmon River. Detection efficiencies of over 90% for both upstream and downstream migrants were achieved when the system was at full development. During and after our experience at Rattlesnake Creek, instream detection sites proliferated in the Columbia Basin and beyond. Since the early instream efforts, many advancements have occurred in both PIT-tag and transceiver capabilities and antenna types, construction, and anchoring methods. Although some challenges faced at Rattlesnake Creek, such as flood flows, antenna damage, noise issues, and power considerations still face instream operators, the technology and construction advances have allowed practitioners to monitor habitats, including large rivers, with innovative methods and at scales far exceeding our initial goals of monitoring fish movement in a small stream.