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Inter-animal telemetery: The Vemco ‘Business Card Tag’
Principal Investigators: Kim Holland, Carl Meyer & Laurent Dagorn
Project Overview

Galapagos shark school

Figure 1. Schooling Galapagos sharks at Maro Reef, Hawaii

Recent advances in telemetry and data-logging tags have provided important new insights into the movement patterns of marine animals. Despite these technological advances, major gaps remain in our understanding of basic interactions within and among species. For example, although we have successfully quantified the movement patterns of a wide variety of sharks and fishes, in most cases we know very little about when, where and how frequently these animals encounter one another during their travels. This type of information could have profound implications for understanding and modeling the movements of marine fishes. For example, we have only a rudimentary understanding of the cohesion dynamics of fish schools and this limits our ability to predict how species such as tunas will move through a seascape. We need a better understanding of individual fidelity to schools and the frequency, and circumstances, of interchange between schools. Related questions include how important information, such as the location of productive foraging areas, is transmitted between marine animals.

Mobile peer-to-peer (MP2P) technologies offer new opportunities not only for characterizing interactions among animals but also for retrieving data about these events and the environment in which they are occurring. A peer to peer network is a system where information passes direct from one peer to another rather than through a central hub. In a mobile peer to peer network some of the peers move around. This technology could help biologists in two main ways: (1) by providing multiple potential paths for data retrieval, and (2) by providing novel information about important biological interactions such as how long individuals within a school stay together, how often animals encounter potential predators, and when and where are mating events occurring.

For our proof of concept study we utilized the Vemco Business card tag (or BCT - see Fig 2 below) to create a very simple peer-to-peer network. The BCT combines both listening receiver and transmitter in a single device, and cycles between listening and transmitting it’s own unique ID code. BCTs are compatible with the Vemco passive monitoring system. They can detect other Vemco coded transmitters, and can themselves be detected by stationary receivers. In its current format, the BCT must be recovered to retrieve data collected.

BCT on Galapagos shark



Click on the image at left to view video of a BCT-equipped Galapagos shark visiting the shark cage diving site.

Figure 2. Vemco Business Card Tag deployed on Galapagos shark, Oahu, Hawaii.

Research Questions
Our first question, was ‘Will it work in the real world?’ Specifically we wanted to determine:
  1. How transceiver duty cycle influences detection efficiency
  2. How frequently BCT-equipped animals detect one another
  3. How we might establish where encounters are taking place
In May 2008, we equipped 4 Galapagos sharks with externally attached BCTs at the site of an ongoing study of shark movements around a cage diving site off the north shore of Oahu (Hawaii - Figure 3). This study site already had 32 sharks instrumented with conventional V16 coded transmitters, plus a listening array of fixed underwater receivers. Additional receivers were already deployed elsewhere around Oahu and throughout the Hawaiian chain. Thus our overall experimental design (Figure 4) allowed BCT-equipped sharks to: (1) Detect one another, (2) Detect other sharks equipped with conventional V16 transmitters, and (3) Be detected by fixed receivers stationed at various locations around the island of Oahu and elsewhere.

BCT Study Site

Figure 3. island of Oahu showing locations of acoustic receivers (yellow points) and capture site of Galapagos sharks equipped with Business Card Tags.

BCT Experiment Design Schematic

Figure 4. Schematic illustrating information flow between different entities within the BCT network.

Two BCTs were recovered from Galapagos sharks after 20 and 132 days at liberty respectively. Recovered BCTs had recorded 4,506 and 4,875 detections of 28 and 30 transmitter-equipped sharks each. Both tags had multiple detections of all other BCT-equipped Galapagos sharks (e.g. Figure 5). BCT data combined with detections from the array of fixed VR2 receivers revealed that BCT-equipped sharks spent periods of days or weeks associated with the ecotourism sites where they were captured and one shark also swam past receiver stations on Fish Aggregating Devices up to 30 km away from these locations. Comparison of detections made by these tags with those made by a fixed array of standard VR2 receivers indicated that the BC tags accurately captured the ‘presence-absence’ patterns of the other tagged sharks. Importantly, the BC tags detected sharks that were beyond the range of the fixed receiver array. The results indicate that the BC tag/MP2P approach can elucidate important inter and intra specific interactions among individuals in areas remote from traditional fixed receiver arrays.

BCT Results

Figure 5. Abacus plots showing detection dates of BCT and V16-equipped sharks. TOP: Detection dates of 4 BCT-equipped sharks by VR2s stationed at ecotourism sites (vertical lines) and offshore Fish Aggregating Devices (crosses). MIDDLE: Detection dates (vertical lines) of BCTs #1, #2 and #3 by BCT #4. BOTTOM Detection dates of V16-equipped sandbar (red) and Galapagos (blue) sharks by BCT #4.
Future Business Card Tag Research
Our future goals include: (1) Developing a transmitter 'beacon-grid' to allow for more precise geopositioning of BCT-equipped sharks and fishes, and (2) Using the BCT system to quantify predator-prey interactions between tiger sharks and sea turtles.
Project Publications
Holland KN, Meyer CG, Dagorn LC (2009) Inter-animal Telemetry; Results from First Deployment of Acoustic “Business Card” Tags. Endangered Species Research. 10: 287–293. DOI: 10.3354/esr00226
Project Sponsors
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