A10. Radio telemetry

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Radio tag © Scimabio Interface

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1. Objectives

Radio telemetry can be used to:

  • Evaluate habitat and utilisation of tributaries, fish behaviour and home range over long river reaches (Cooke, Bunt and Schreer, 2004).
  • Study fish migration and spawning ground locations.
  • Evaluate fishway passability, river continuity and fish behaviour facing dams ) and discharge events (Larinier et al., 2005; Leander et al., 2019; Mameri et al., 2019).

2. Method summary

The goal of radio telemetry is to determine fishes’ free-swimming position through active tag emitters. The signal is received by autonomous receivers (passive tracking), or a mobile station (active tracking with a boat, car, aircraft, or by foot) (DeCelles & Zemeckis, 2013; Thorstad et al., 2013). Fish are either netted or trapped, then anesthetised and tagged with an active tag (carrying an emitter and powered by a battery). It requires a handling survey and often a surgical operation, a complex and specialist process. An antenna allows for the transmission of data to the receivers. The tag can be external or implanted within the fish, either in the body cavity or, less frequently, in the oesophagus (Steinbach et al., 1986). Depending on the tag position the tag antenna can be ejected out of the fishes’ body through the surgical scar, mouth or gill.

Antenna receiver © Scimabio Interface

The tag should be adapted to species, stage, and size to avoid ‘fallback’ and bias in fish behaviour (Frank et al., 2009), but this is not always possible. Several types of emitters exist and their lifespan is directly linked to the battery size, which is the main component. The minimum size of a tag is around 1 cm with a weight of 0.5 g, and a lifespan of four weeks. Larger tags can weigh several grams and operate for more than a year. The emission of Very High Frequency (VHF) is between 27 and 300 MHz (Karp, 2014). The reception antenna can be underwater or aerial, but is limited in deep water habitats. Emitters can be coded or non-coded.

Coded tags mean that all transmitters emit on the same frequency with an added ‘pulse code burst’. This identifies each tag individually due to unique patterns in pulse rate. The use of this type of tag is necessary in instances where several individuals are likely to pass simultaneously near the receiver, e.g. during the migration of large quantities of fish. During migrations as many as 100 fish can pass a point in a river in less than 10 seconds, but by using coded tags the probability of miss counting fish is significantly reduced. However, since coded tags deliver three or more distinct pulses to transmit their code, their energy consumption is significantly higher and battery lifespan shorter compared to that of non-coded tags. Special receivers for coded tags are necessary to decode the signal and record data.

Non-coded tags emit on slightly different frequencies and are more adapted to study the (migration) behaviour of fish in lower quantities. The receiver scans one frequency after another, which are all in a defined frequency range and spaced at 10 kHz. A ‘beep’ sound is emitted when a tagged fish is in the detection area. The non-coded survey restricts the number of tagged fish to around 40 individuals, since the receiver’s scanning time is longer. This increases the probability of missing a target, especially rapidly swimming fish. To compensate for this, the receivers usually cover a large area. Some emitters can be set to minimise battery use and a mortality option (indicating that the fish is no longer moving) can be included by programming a doubling of the ‘beep’ detection sound (Tétard et al., 2015). When a fish passes through the detection area, the frequency, date, hour, signal intensity and sensor data is transmitted.

Biologging allows for interdisciplinary research through thermo sensors, deep sensors, activity or physiological sensors linked to the transmitter (Cooke, 2008). In theory, this data can also be transmitted through the normal radio tracking process.

Depending on the manufacturer, receivers can be directly plugged into the domestic power supply or be powered by a (usually solar powered) battery. The latter is useful for working in remote areas without a power supply. The locations of recording stations are fixed and should be selected based on the purpose of the study, ease of deployment and access and protection from vandalism. Receiver location and reception signal are crucial for reliable data.

3. Advantages

  • Well-known technique with a wealth of background information.
  • A wide choice of tag size and capacity available.
  • Fish can be tracked over different timescales, from several weeks to up to a year.
  • Long detection ranges and less disturbed by turbulence than acoustic tags.
  • Powerful in shallow areas.
  • Receivers can be set on the bank, making it easy for one person to download the data.
  • Possible to survey with a mobile antenna placed in a car, by walking or in an aircraft.
  • Suitable for very large rivers.
  • Advances in reducing tag size make the technique suitable for a large range of species including those that are challengingly shaped, e.g. eels (Hanzen et al., 2020).

4. Disadvantages

Atlantic salmon tagging © Scimabio Interface
  • Expensive technique.
  • Tagging and deployment of recording stations is labour intensive, though maintenance requires only one person.
  • Some vehicles carrying mobile receptors can cause strong disturbances.
  • Size of the emitter, lifespan and range are related to battery size.
  • Functions poorly when conductivity is very high, and the river is deep.
  • Need a special permit for surgical procedures on fish.
  • Fish position is less precise compared to acoustic telemetry.
  • Sensitive to noise (ship and car engines, electric wires, source of radio frequencies).
  • Not suitable for estuaries or studies in the sea.
  • Data analysis is expensive.
  • Detection issues where there are large obstacles (e.g. bridges, high riverbanks etc.).
  • Receiving capacity also related to water conductivity.

5. Coded tags advantages/disadvantages

Advantages of coded tag

  • Can track several fish simultaneously.
  • No scanning times.

Disadvantages of coded tag

  • In case of very high fish density in a short period of time, conflict in emitters can lead to the receivers missing fish.


Advantages of non-coded tag

  • Receiver and tag price are usually lower.

Disadvantages of non-coded tag

  • Not suitable for large numbers of migrating fish.
  • Detection area must be large enough to repeatedly detect a single fish swimming quickly and must be adapted to time scanning.

6. Recommendation for method application

  • Be aware of the ability of your targeted species to support the tag size.
  • Avoid surgical implantation when intragastric tagging. Method of tagging should be appropriate to the species, study objectives and follow ethical and legal procedures at every step.
  • Test the range of each receiver relating to your need (e.g. overlap or not, range detection) and sources of interference (electric line, roads, etc.).
  • Always set a receptor at the furthest point of the study area downstream to record the downstream movements of fish. This is particularly important for species that have a large foraging range (Steinbach et al., 1986).
  • Protect your equipment from vandalism as it results in unwanted expenses and loss of data.
  • Orientation of the receiver’s antennas is crucial as it influences the signal strength (David & Closs, 2001).

7. Costs

Very expensive method, costing tens of thousands of pounds. Cost is related to the number of receivers, number of fish tagged, protection of the equipment against vandalism, and the time allocated for mobile surveying.

8. Protocol and data analysis

A wide range of methods exist to conduct spatial data analysis. The accuracy of the behaviour analysis required depends on the study objective. In the case of a simple fishway passability study, analysis is related to time and fish speed between two receivers (upstream and downstream of the obstacle), time between the bottom and top of a fishway, time between two obstacles etc.

Analysis complexity depends on the protocol and the array designed. https://www.researchgate.net/publication/322212349_An_Analysis_of_Triangulation_Techniques_for_Radio-Telemetry https://www.researchgate.net/publication/270762030_Acoustic_and_Radio_Telemetry

9. References

  1. Allen, J. (2009) ‘Use of Coded Transmitter Schemes to Overcome Radio Frequency Spectrum Constraints in Terrestrial Wildlife Tracking .’, Report Advanced Telemetry Systems, Inc., Isanti, MN 55040pp. 1–7.
  2. Cooke, S. J. (2008) ‘Biotelemetry and biologging in endangered species research and animal conservation: Relevance to regional, national, and IUCN Red List threat assessments’, Endangered Species Research, 4(1–2), pp. 165–185. doi: 10.3354/esr00063.
  3. Cooke, S. J. et al. (2008) ‘Developing a Mechanistic Understanding of Fish Migrations by Linking Telemetry with Physiology, Behavior, Genomics and Experimental Biology: An Interdisciplinary Case Study on Adult Fraser River Sockeye Salmon’, Fisheries, 33(7), pp. 321–339. doi: 10.1577/1548-8446-33.7.321.
  4. Cooke, S. J. et al. (2004) ‘Understanding Fish Behavior, Distribution, and Survival in Thermal Effluents Using Fixed Telemetry Arrays: A Case Study of Smallmouth Bass in A Discharge Canal during Winter’, Environmental Management, 33(1), pp. 140–150. doi: 10.1007/s00267-003-0175-2.
  5. David, B. O. and Closs, G. P. (2001) ‘Continuous remote monitoring of fish activity with restricted home ranges using radiotelemetry’, Journal of Fish Biology, 59(3), pp. 705–715. doi: 10.1006/jfbi.2001.1684.
  6. DeCelles, G. and Zemeckis, D. (2013) Acoustic and Radio Telemetry, Stock Identification Methods: Applications in Fishery Science: Second Edition. doi: 10.1016/B978-0-12-397003-9.00017-5.
  7. Frank, H. J. et al. (2009) ‘What is “fallback”?: Metrics needed to assess telemetry tag effects on anadromous fish behavior’, Hydrobiologia, 635(1), pp. 237–249. doi: 10.1007/s10750-009-9917-3.
  8. Hanzen, C. et al. (2020) ‘ Surgical implantation of radio tags in three eel species ( Anguilla spp.) in South Africa’, Journal of Fish Biology. doi: 10.1111/jfb.14270.
  9. Karp, C. (2014) ‘Summary of Freshwater Fisheries Telemetry Methods’, (October), p. 24.
  10. Larinier, M. et al. (2005) ‘The use of radio telemetry for optimizing fish pass design’, in Aquatic telemetry: advances and applications. Ustica Italy, pp. 53–60.
  11. Leander, J. et al. (2019) ‘The old and the new: evaluating performance of acoustic telemetry systems in tracking migrating Atlantic salmon (Salmo salar) smolt and European eel (Anguilla anguilla) around hydropower facilities’, Canadian Journal of Fisheries and Aquatic Sciences.
  12. Mameri, D. et al. (2019) ‘Passability of Potamodromous Species through a Fish Lift at a Large Hydropower Plant (Touvedo, Portugal)’, Sustainability, 12(1), p. 172. doi: 10.3390/su12010172.
  13. Steinbach, P. et al. (1986) ‘Radio-pistage de grandes aloses adultes en Loire’, Bulletin Français de la Pêche et de la Pisciculture, 302(302), pp. 106–117. doi: 10.1051/kmae:1986007.
  14. Tétard, S. et al. (2015) ‘Marques actives utilisées en télémétrie "poissons "’, in Marques actives utilisées en télémétrie "poissons".
  15. Thorstad, E. B. et al. (2013) ‘The Use of Electronic Tags in Fish Research - An Overview of Fish Telemetry Methods’, Turkish Journal of Fisheries and Aquatic Sciences, 13(January), pp. 881–896. doi: 10.4194/1303-2712-v13.
  16. http://www.ramp-alberta.org/ramp/community/telemetry.aspx