Overview of the Performance of PIT-Tag Interrogation Systems for Adult Salmonids at Bonneville and McNary Dams, 2002.

Abstract

During winter 2001, the U.S. Army Corps of Engineers (Corps) and Bonneville Power Administration (BPA) installed a prototype orifice-based PIT-tag interrogation system into the Washington Shore Ladder at Bonneville Dam (BWSL). Detectors were installed into 12 weirs: 4 downstream (Weirs 334-337) and 8 upstream (Weirs 352-359) from the fish release point (i.e., the exit ladder for the Adult Fish Facility). NOAA Fisheries (National Marine Fisheries Service--NMFS) tagged and released salmonids during 2001 to determine tag-reading efficiencies for different salmonid populations. Data analyses focused on the upper eight weirs. The 2001 tagging results for spring chinook salmon indicated that having detectors in four consecutive weirs would have been sufficient to yield a reading efficiency of 95%. The BWSL orifice-based system performed well until the coho and fall chinook salmon migrations began. Coho and fall chinook salmon appeared to use the weir overflows, and thus avoid detection, at much higher rates than biologists expected. During 2001, technology advances led to the development of significantly larger antennas than had been available earlier, and thus it was possible to build antennas of approximately 2 x 6 ft. Consequently, it became feasible to design interrogation systems for ladder locations where all fish would have to go through the antennas and thus could not avoid detection by using the weir overflows (Fig. 1). Destron Technologies by Digital Angel designed a prototype interrogation system with two antennas that was installed into the counting-window area in the Oregon Ladder at McNary Dam, where its performance could then be directly compared to that of the orifice-based system in the same ladder. Although the orifice-based systems appeared less effective than the fisheries community wanted for fall chinook and coho salmon, the decision was made to proceed with installations planned for Bonneville and McNary Dams because valuable data would still be collected. During the winter of 2002, the Corps and BPA installed PIT-tag interrogation systems into the Bradford Island and Cascades Island Fish Ladders at Bonneville Dam and into the Washington and Oregon Ladders at McNary Dam. Like BWSL in 2001, these ladders had eight weirs (16 orifices) outfitted with fiberglass antennas. Douglas County Public Utility District also installed an orifice-based system into its ladders at Wells Dam, but they were able to use weirs with no overflow sections wherein all fish had to swim through the orifice antennas. Thus, 2002 was the first year that the fisheries community had PIT-tag detection of adult salmonids at Bonneville, McNary, Wells, and Lower Granite Dams (Fig. 2). This overview will provide information on how well the systems at Bonneville and McNary Dams performed.