Development and use of a large, flexible antenna to detect fish implanted with passive integrated transponder tags

— A novel antenna design has been developed to detect fish implanted with full-duplex passive integrated transponder (PIT) tags. The antenna is constructed of light-weight flexible hose and measures 2.4 by 6.1 m, providing a substantially larger reading range than other PIT antennas. Herein, we describe its use in a small instream monitoring system to detect migrating smolts of steelhead ( Oncorhynchus mykiss ). During testing, the combined detection efficiency for the 2 arrays of antennas with the new design was 97%, which is comparable to efficiencies of standard antennas made with polyvinyl chloride or high-density polyethylene. The lightweight, flexible design of the new antenna affords relatively easy transportation and deployment compared with that of rigid antennas, and smaller crews and vessels are needed for its maintenance and deployment. The development of the flexible antenna has expanded the utility of PIT technology by increasing the scope of potential sampling applications to a wider range of habitats and environmental conditions.