A new low-cost instream antenna system for tracking passive integrated transponder (PIT)-tagged fish in small streams

We present a new, low-cost, low-power, half/full-duplex passive integrated transponder (PIT) tag interrogation antenna for use in detecting fish movements in small streams. New technology by Allflex-USA allowed us to develop a reading system with an antenna 279.4 cm wide x 60.9 cm high that reads both common tag types used in fisheries today for about US$1,000. An instream antenna of this size and price makes high-resolution tracking of fish movement in small streams feasible where cost and tag-type restrictions were prohibitive. For evaluation, we placed the antenna upstream of a small estuary on the central California coast to observe the diel movements of juvenile steelhead Oncorhynchus mykiss between the estuary and upstream habitats in both spring and fall months.