Researchers often use technology to track the movements of animals. And although whale sharks are the planet’s largest living fish, relatively little is known about these ocean travelers. Tagging animals can help communicate key information about these unpredictable and mysterious marine giants – like distinct migration patterns, feeding behaviors and climate change responses.
Not all tracking tags are the same. “The ‘archival’ or PSAT type record sunrise and sunset times,” says Dr. Alistair Dove, Senior Scientist at the Georgia Aquarium. “When the tag pops off, it uplinks the data via satellite. If you know when and where you deployed the tag, you can calculate from the data how far the animal has moved and in what direction by the shifts in sunrise/sunset times (its kind of tedious and not all that accurate). These tags also record temperature and depth up to 1,800 meters.”
But Smart Position or Temperature transmitting tags – known more commonly as SPOT – are more advanced pieces of GPS technology. Every single time a whale shark surfaces, the SPOT tag beams valuable information – such as precise location data – to a satellite in real time. The satellite then communicates this data to the project researcher.
SPOT tags are usually “tethered to the animal on a line such that if the animal is at the surface, the tag is floating above it and reporting to the satellites,” says Dr. Dove.
During the tagging process, researchers able retrieve skin tissue biopsies to build our knowledge of whale shark biology. Rafael de la Parra, a lead whale shark biologist and core researcher for Project Domino, has tagged and biopsied over 700 whale shark individuals.
He explains that when you attach a tag to a whale shark “you stretch a rubber band and hold firmly the pole, and then aim and shoot. On average, the whale sharks do not even notice [being tagged] 70% of the time. From experience, it is always better and easier to do it from behind [the animal] in a tangential angle to get through the dermal denticles – about 10 centimeters is the max penetration, considering the skin thickness, and about 20 or more centimeters resembles an intradermic shot vaccine… We call them ‘expensive piercings.’ “
According to de la Parra, many researchers prefer to re-use the satellite transmitters after they have been deployed for three or more months, with six months being an ideal duration of time.
“Archival tags are the top ones – they are programmed to pop up [to the surface]” after a specific period of time,” de la Parra says. These tags offer “invaluable information if retrieved around the programmed date, because if you connect this one to a computer, you can download minute-by-minute information of where these whale sharks were, how deep they dove, and what temperatures were surrounding the animal.”
Conventional tags aren’t nearly as fancy (or expensive) but still offer researchers helpful information. These yellow plastic placards have a consecutive number that help identify a whale shark as it migrates through different bodies of water.
People can even follow satellite tagged animals online, such as Sara, a whale shark that was recently tagged by Dr. Robert Hueter, the Director of Mote Marine Laboratory’s Center for Shark Research.
Data from whale shark tracking tags helps build an overall understanding about these animals’ unique global movements, ultimately helping to conserve the species.
Find out more about my experience studying this species in the wild with this case study on researching wild wild sharks.
Photo Credits: Alistar Dove, Rafael de la Parra and Jennifer Mckinney.
Video Credit: Georgia Aquarium