A new electronic tag developed by ESA and other partners has been attached to four tiger sharks in the Caribbean in a test of a new satellite-connected fish tracking system. Described by the space agency as cheaper and more animal friendly, the new tags will help to monitor the sharks' migration patterns for years.

Tracking the migration behavior of fish is one of the most basic and powerful tools for ichthyologists and other scientists. The problem is that many species have very complex migration patterns that stretch over thousands of miles and only become apparent after many years of mapping.

This means that the old method of stapling a metal tag on a dorsal fin and hoping that it will be found and turned in by some conscientious fisherman isn't quite up to the job anymore. Instead, researchers have relied on more and more sophisticated electronic tracking tags that can either record or transmit data in much more detail over a much longer timeframe.

However, such tags have their own limitations. Not the least of these is that they tend to be very large, heavy, expensive, and only have so much battery power. Based on the Artic microchip developed by ESA along with AnSem in Belgium, the new tag was built by Iceland's Star Oddi and is designed to be smaller, cheaper, and much more energy efficient.

The tags were attached to the four shark subjects by an expedition from the Dutch Elasmobranch Society, the Saba Conservation Foundation, and Nature Foundation Sint Maarten. Once deployed, the tags started recording the depth the sharks dove to, temperature, light level, and angle to aid in 3D mapping.

The goal is to track the tiger sharks for years to gain a better understanding of how they migrate and where they breed. This will not only provide academic knowledge, but also help in conserving the predators, which are under threat. The tags gather data and then periodically transmit a radio "handshake" signal to the Argos satellite monitoring system in France. This brief signal uses only as much power as a mobile phone text, so the tag can conserve its battery until contact is made. It then transfers its data and when complete, the satellite sends a confirmation signal, so the tag doesn't need to transmit for longer than necessary.

According to ESA, this system increases the battery life by a factor of five. In addition, the tag holds more information than previous versions and can be ordered to clear its memory after transmission to free up space for more.

"The two-way link with the satellite is the key," says ESA's Peter de Maagt. "The increased efficiency has had knock-on benefits that have opened up new opportunities for better, less invasive tracking. This makes it easier to monitor how wildlife is coping in our fast-changing environment."

Source: ESA

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