Northwest Fisheries Science Center

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Document Type: Contract Report
Center: NWFSC
Document ID: 1319
Title: Detection efficiency of a passive integrated transponder (PIT) tag interrogator for adult Chinook salmon at Bonneville Dam, 2005
Author/Editor: Brian J. Burke, M. A. Jepson, Kinsey E. Frick, C. Peery
Publication Year: 2006
Publisher: National Marine Fisheries Service
Contracting Agency: Portland and Walla Walla Districts, U.S. Army Corps of Engineers. Portland, Oregon
Project Number: ADS-00-14
Pages: 24
Date: December 2006

During winter 2004-2005, we tagged over 700 adult Chinook salmon in 2005 with both a radiotelemetry tag and a PIT tag to determine detection efficiency of the vertical-slot PIT-tag interrogator, which was installed in the Washington Shore Fish Ladder at Bonneville Dam (site code BO4).  Detection efficiency of BO4 was very high during spring (cumulative efficiency of 100%), when water temperatures were relatively low.  However, efficiency was slightly lower in fall (cumulative efficiency of 96%), partially due to higher water temperatures and partially to the types of PIT tags used.  Differences between efficiencies recorded during spring and fall may also be due to behavioral differences between runs of Chinook salmon, though we did not specifically test fish behavior in this study.  The rate of false positives for dam passage was reduced by the inclusion of the BO4 interrogator.  Furthermore, overall interpretation of PIT-tag data was improved when we altered our algorithm for assigning passage using PIT-tag data to interpret fish passing the Washington Shore Ladder only when fish are last detected at one of the BO4 coils.  However, this requirement may be dropped if cumulative detection efficiency at BO4 drops below 96%.