Social sharks: UD researchers monitoring animals’ travels, ‘networks’
Written by
Molly Murray
The News Journal
Somewhere off the south Atlantic coast, a school of slate-gray, high-tech sand tiger sharks is swimming around, emitting a pinging signal of their own existence while also recording data from the marine life around them.
University of Delaware assistant professor of oceanography Matt Oliver calls it shark social networking.
The project is so unique and risky that traditional sources of research money weren’t available to test the idea that you could use one type of marine life to monitor other species in the same environment – a vast world where it can be difficult and costly to keep tabs on a single species, let alone a group of animals that coexist in the ocean.
Oliver, who hosts an open research lab at the university’s College of Earth, Ocean and Environment in Lewes, was showing off the remote sensing technology that he and his graduate students use when a visitor asked if there was an innovative but risky project that needed research funding.
So Oliver contacted assistant professor of fisheries Dewayne Fox at Delaware State University, and the two came up with a shark-tagging program that started last summer in the Delaware Bay and, if all goes as planned, will conclude there later this year.
Therein lies the catch – literally.
To recover the data, the researchers and their students must capture the sharks and remove the listening devices, Fox said.
If you’ve ever tried to catch any fish, let alone a specific fish, you can imagine the challenge.
But Oliver and Fox have an electronic edge.
For years now, Fox has been monitoring sharks and Atlantic sturgeon in the region using a series of listening stations that gather data from species with transmitters implanted in their bodies.
So he knows when sand tiger sharks arrive in the Delaware Bay and where they congregate and feed. He knows there are key hot spots. Plus, Oliver said, Fox has a phenomenal sense about where to look for the species he is targeting for research and the optimum gear needed to collect them.
Oliver also has an underwater robot called a glider – a kind of a mini yellow submarine – that he can use to listen to the transmitters pinging and track the movement on a computer.
The research involves three different types of tags. One is an acoustic transmitter that pings receivers while passing by a set of 70 devices situated mostly in the Delaware Bay, with a few along the Atlantic coast. The receivers are maintained by Fox, who has tagged more than 500 sharks since 2006.
The team is using pop-off satellite archival tags, which store data on the sharks’ journeys for one year and then automatically release from the animal to dispatch a location signal for retrieval from the water.
The newest type of tag both transmits and receives information to communicate the shark’s location and hear the pings of other sharks, fish or marine mammals that also have acoustic tags.
“It will tell us not only where it is, but who it’s with,†Oliver said.
In all, 22 sharks have the full array of tags, Fox said.
Tagging marine species with radio transmitters – the smaller device with a specific signature – is nothing new. And that’s what makes this project possible.
“Now there are so many tags out there†that the sharks could be picking up lots of interesting data from other species – “Matt’s social network for sharks,†Fox said.
But the project is more than just cutting-edge research. First, it is a test of the idea that you can, using electronic tracking and monitoring, recapture tagged animals and recover data. Second, if it works, there is the possibility of figuring out where animals travel and how they interact with other species.
“The larger question we’re trying to get at is how an organism interacts with its environment,†Oliver said. That can be a difficult question to answer “in a place like the ocean that is always moving and always dynamic.â€ÂÂÂÂÂÂÂ
For instance, they could learn whether sharks choose set migration routes or if their movement is random.
The data also could give resource managers information on when and where you are likely to find species – information that could ultimately be used to target or protect ocean fisheries, he said.
“The sort of data we’re getting, nobody has,†Oliver said.
In the end, it will help “drive home the connections†between marine animals and their environment, he said.
Several months into the program, Danielle Haulsee, one of Oliver’s Ph.D. students, tracked the movements of some of the sand tiger sharks using the glider, which is programed to follow a specific route. Off the coast of the Delmarva Peninsula, she picked up the pinging from the tagged sharks.
“We never heard from the same shark twice,†she said.
Shark researchers in the region recognize that while some shark behavior is predictable – especially in places like the Delaware Bay where sand tiger sharks come to give birth – it can also be surprising.
Take the 16-foot-long, 3,400-pound white shark Mary Lee. The female shark was outfitted with a satellite tag off Cape Cod in September, and researchers have been following her curious travels ever sense.
Over the course of several months, she’s traveled as far south as Jacksonville, Fla., where she ended up close to the surf zone, in the near-shore waters of Ocracoke, N.C., and then, a week ago, about 40 miles off the Delaware and New Jersey coasts. She is now back in New England waters.
Greg Skomal, with the Massachusetts Division of Marine Fisheries, was part of the team that tagged Mary Lee with something called a SPOT tag, which transmits locations to a satellite. The technology uses Doppler-based geoposition technology to track marine animals like white sharks, he said.
Skomal said his goal is much like what Fox is trying to figure out: the movement and patterns of sharks, where they are spending time and what the criteria are for their survival.
The first step, he said, is figuring out where they are going.
Mary Lee’s movements back to northern waters is a surprise because of low water temperatures in New England, he said. While white sharks can regulate their body temperatures for a prolonged and deep dive into colder water, no one is certain what prolonged exposure will mean.
But one thing is certain, Skomal said: She is looking for something, and she hasn’t found it yet.
Skomal had worked with white sharks before, but in the past, he had always had a cage between himself and the shark. With Mary Lee, the team worked directly with the animal – made famous by the movie “Jaws.â€ÂÂÂÂÂÂÂ
“They’re massive, amazing,†he said. “It makes you feel insignificant.â€ÂÂÂÂÂÂÂ
Meanwhile, the sand tiger sharks that Fox and Oliver are tracking are species of concern.
There hasn’t been a formal stock assessment, said National Oceanic and Atmospheric Administration Fisheries Service research scientist John Carlson.
Estimates of population decline range from 25 to 75 percent, he said.
Carlson said that with better tracking, scientists may one day learn more about the most critical habitats for these sharks – most particularly where key nursery areas are.
