searching for Argos tag with goniometer
21.09.2022 Animal tracking applications

Lost shark tag found thanks to the Animal Telemetry Network and the Argos goniometer

Marcus Drymon, Assistant Extension Professor at Mississippi State University Marine Fisheries Specialist and Dr. Greg Skomal, an accomplished marine biologist who we interviewed for Shark Week, were recently able to recover a lost shark tag thanks to NOAA’s Animal Telemetry Network (ATN) and an Argos goniometer loaned by CLS Group’s American office, Woods Hole Group. Here, they share their story of how a community came together and were able to recover the tag, and more importantly the data inside.

Spring winds in the northern Gulf of Mexico bring ashore a treasure trove of items for the curious beachcomber. While driftwood, shells, and sea glass abound, the persistent beachcomber might occasionally find a shark tooth – but a shark tag?

great white sharkAs I wrapped up lectures for my May term field course Shark and Ray Biology, I received an email from a colleague in Massachusetts, Dr. Greg Skomal. A few months earlier, Greg had attached a PSAT to a large male white shark (Carcharodon carcharias) off the coast of South Carolina. Unfortunately, the tag had detached prematurely, and was currently 9 miles south of Perdido Key, on the border of Florida and Alabama. “If it washes ashore near you, could you keep an eye out for it?” asked Greg? And so the story begins.

The next day, the tag was moving west and closer to shore, and was just 4 miles off Gulf Shores, Alabama. A day later, the tag was in the Mobile Bay ship channel; the following day, the tag was in the Mississippi Sound and looked like it might make landfall on Little Dauphin Island on Friday.

Friday was also the last day of the Sharks and Rays course. As I administered the final exam to the class, I offered extra credit to anyone who could locate the tag. After completing their test, the Sharks and Rays students headed to the beach. Hours passed, and the tag had yet to be located. On Sunday, my students and I spent several hours scouring the beach, but to no avail. “Is it possible to find a beached PSAT without a goniometer,” I asked Greg? At this point, Greg reached out to NOAA’s Animal Telemetry Network and the Woods Hole Group, and a goniometer was overnighted.

Discover the Argos goniometer

 

found Argos tagThe goniometer, a special receiver that can detect satellite tag “pings,” arrived the next morning, and we went back to Little Dauphin Island for one final search.

With the sun sitting low in the sky, my son and I were joined by Mendel and Brian from the Dauphin Island Sea Lab. Together, the four of us walked the edge of the marsh grass with the goniometer. As the signal got stronger, we strained our eyes for any sign of the tag that had eluded us for nearly a week. As we neared a large clump of flotsam, Mendel leaned over for a closer inspection when something shiny caught her eye. Incredibly, she had located the tag buried under a pile of dead marsh grass!

As we shared our triumphs with Greg, we were surprised to learn that rather than heading north as expected, the white shark tagged off South Carolina had moved south and into the Gulf of Mexico.

Thanks to the goniometer (and Mendel’s keen eyes), we hope to gain a better understanding of the fine scale behavior of this unique individual.

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