Researchers at University of Delaware and Delaware State University have new findings on the sand tiger shark, after deploying robotic drones to track them three years ago.
The study was published at the end of May in the journal Marine Ecology Progress Series.
The sand tiger shark is recognized internationally as a vulnerable species, as its numbers have largely been reduced by overfishing. To gain a better understanding of the sand tiger sharks’ migratory patterns and habitat preferences, local scientists have tagged them and tracked their activity with a drone.
Danielle Haulsee, a PhD candidate at UD and lead author on the study, says that the sharks wear acoustic tags, as opposed to GPS tags, which aren’t compatible with marine animals.
“GPS tags don’t work very well because the antennae of a GPS tag needs to be out of the water. So something like acoustic telemetry that works in the water is more useful for studying a species like [the sand tiger]," said Haulsee.
The technology has revealed that the sand tiger sharks like to remain close to shore and in the fall, they travel in low salinity waters, particularly the freshwater plume from the Delaware Bay. They also prefer habitats containing lots of dissolved plant and animal material.
“That's the stuff that makes the coastal waters a little yellowish, it makes the water a little dirty," described Haulsee.
Haulsee said it’s likely the sand tiger sharks go to these areas in search for food, or they could also be simply drawn by the scent of these materials.
As Haulsee and her fellow researchers continue to analyze the shark’s migration patterns, she hopes to eventually develop a probability map based on data collected by the drone. The map, she says, would ideally show a fishermen where sand tiger sharks are most likely to show up on any given day.
“[Fishermen] can look at this map almost like a weather forecast, and say, ‘Well, sand tigers are likely to be here today because of the conditions so maybe if I fish a little bit in a different area, then I’ll be less likely to encounter sand tigers,'" said Haulsee.
With more fishermen dodging the sand tiger sharks, perhaps their numbers might come surging back.
