Efficacy of 12-mm Half-Duplex Passive Integrated Transponder Tags in Monitoring Fish Movements through Stationary Antenna Systems

Abstract

Globally, many freshwater fishes are declining in distribution and abundance, but for many species conservation measures are hindered by a limited knowledge of their ecology. Recent development of 12-mm half-duplex (HDX) passive integrated transponder (PIT) tags has broadened the potential application of this technology for studying habitat selection and migration of freshwater fishes. However, the limited read range of the smaller 12-mm PIT tags can limit their functionality in ecological studies. The present study used four migratory fish species to test the efficacy of different PIT antenna designs for detecting 12-mm HDX tags in small- and medium-sized rivers. Three types of pass-through antennae were created and coupled to either a single reader or multiplexor board. Across single-reader and multiplexor systems, the detection efficiencies for Giant Kokopu Galaxias argenteus, Shortfin Eel Anguilla australis, and New Zealand Longfin Eel Anguilla dieffenbachii ranged between 87% and 97%. Adult Pouched Lamprey Geotria australis also had a high detection rate of 74%, even though several other migration routes existed that were unmonitored. Overall, the present study shows that with appropriate antenna design, the 12-mm HDX PIT tag can be effective for monitoring a variety of fish species. Although the antennae in the present study had a maximum width of 6.1 m, the spaced double-coil antenna design may increase efficacy of the 12-mm tag in larger rivers.

Received April 27, 2017; accepted September 1, 2017 Published online October 30, 2017

ACKNOWLEDGMENTS

We would like to thank all National Institute of Water and Atmospheric Research staff who have assisted with the fieldwork involved in this project, particularly Josh Smith and Rimu Wharakura. We also appreciate the support of local landowners who allowed access through their property and supported the installation of telemetry equipment. This study was funded by the New Zealand Ministry of Business Innovation and Employment, contract CO1X1002.