Radio frequency identification with passive integrated transponder (PIT tagging)

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Quick summary

Figure 1: two radio transmitters of different size
Figure 2: radio telemetry receiver.
Figure 3: Brown trout (Salmo trutta) with a radio transmitter in the body cavity and the external antenna.


Date:

Type: Tool

Suitable for the following [[::Category:Measures|measures]]:

Introduction

RFID (Radio Frequency Identification) system uses PIT (Passive Integrated Transponder) tags to detect and follow individuals. The PIT tags (Figure 7), each with a unique alphanumeric code, are of small size and benefit of indefinite operational life (no battery is required). When entering in the detection area of a RFID antenna (Figure 8), the reader is responsible of powering and communicating with the tag. The tag antenna captures energy from a tag and transfers the tag’s ID.

Low Frequency RFID uses magnetic fields that can go through water in contrast to high frequency RFID. Owing to the shorter detection range (less than 2 m perpendicular to the antenna plane) RFID technology is mainly suitable for smaller systems. Two different technologies can be used (source: https://www.oregonrfid.com/resources/hdx-fdx/):

  • Half duplex RFID (HDX): A half duplex RFID reader generates short magnetic pulses that wirelessly charge a capacitor (Figure 9) inside an HDX tag. When the charge field turns off, the tag uses the stored power to send the tag number back to the reader (Figure 10) without interference from the reader.
  • Full duplex RFID (FDX): Full duplex RFID generates a continuous magnetic field which powers the tag to respond immediately. Tags repeat their message, while powered by the field, up to 30 times per second.

The whole system has to be supplied by DC power, powered by different ways:

  • Battery
  • Solar
  • Thermoelectric generator
  • Micro hydro (to charge the batteries)
  • A power supply can transform the AC power to DC power


Application

The RFID technique is used in FIThydro Test Cases in order to follow fishes to study their migration paths, their behaviour and to assess the efficiency of upstream and downstream migration devices and other mitigation measures on habitat. The PIT tag has to be inserted in the fish by surgical act. For this, the fishes are anaesthetized. The tag is inserted either using a syringe or through a small incision in the abdominal cavity or muscle. Most researchers (Jepsen et al., 2005) adhere to the principle that the weight of the tag should not exceed 2 % of the total weight of the fish. As for all experiments with living beings, the regulatory obligation must be respected: the personnel must be qualified, the company/organism must be certified and obtain the agreement of an ethics committee. The 3R rule (replace, reduce, refine) must be applied. This technology allows tagging of very small fishes due to the small size of the tag. It allows following fishes over several years since the tag has no battery and a quasi-endless lifetime. The drawbacks are the size of the antennas and the detection range. Due to the large number of code existing, a large number of fishes can be tagged. It is not sensible to turbidity, or thermal stratification. One threshold is the effect of metal on the detection ranges of the antennas. Indeed metal is disrupting the signal. For example, it will not be possible to install an antenna in a metal baffle fish pass. In FIThydro this technology has been used to assess the efficiency of downstream migration devices (Figure 11), fish passes and fish behaviour systems.

Other information

Radio telemetry is gear-intensive with high initial costs for the equipment, but also for transmitters, the preparation and station installation. Radio telemetry experiments have to be considered as animal experiments and special permissions from the local authorities are needed.

Relevant literature

  • Beeman, J. W., E. E. Hockersmith & J. R. Stevenson. 2012. Design and performance of radio telemetry systems for assessing juvenile fish passage at three hydroelectric dams. Pages 281-302 in N. S. Adams, J. W. Beeman & J. H. Eiler. Editors. Telemetry techniques: a user guide for fisheries research. American Fisheries Society, Bethesda, Maryland.
  • Eiler, J. H. 2012. Tracking aquatic animals with radio telemetry. Pages 163-204 in N. S. Adams, J. W. Beeman & J. H. Eiler. Editors. Telemetry techniques: a user guide for fisheries research. American Fisheries Society, Bethesda, Maryland.
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