How US scientists tagged and tracked 770kg shark

Miss Costa, a white shark, released after being tagged by researchers. Picture / Ocearch.org

She isn't quite an adult, but at 3.8m long and weighing in at just under 1700 pounds (770kg), scientists were eager to tag Miss Costa to follow her feeding and living habits.

They got their chance when the white shark first appeared in late September off the coast of Nantucket in Massachusetts. An added bonus came on Monday when her GPS-like tracking device showed her swimming near the surface just off the coast, east of the Virginia-North Carolina state line.

While it might surprise the average beachgoer to hear that the shark, nicknamed Miss Costa, was spotted along Virginia's coastline, scientists who specialise in studying sharks said it isn't all that rare.

"It's not unusual for white sharks to come into the Carolina area close to the coast in winter time," said Robert Hueter, who is the lead scientist on the expedition run by Ocearch.org, a research operation on sharks.

He said Miss Costa is likely headed to her winter feeding grounds in Florida.

The shark is one of dozens of sharks the group tracks. They are often named for the sponsors involved (Miss Costa is named for Costa Sunglasses).

The information scientists are able to track and glean once a shark is tagged is important, they said, to understanding the animals and helping to preserve their habitat.

Using a 38m boat and a special hydraulic lift, scientists are able to get access to the sharks for a brief time. In about 15 minutes, they take genetic samples, blood and other samples, then attach a transmitter to the shark's dorsal fin.

That transmitter sends a signal to satellites and works almost like a GPS, allowing scientists to track the shark's movements. When the shark swims near the surface, which usually isn't often, the transmitter sends a signal that gets picked up by a satellite. Scientists can then see the shark's location in "pretty much close to real time," said Hueter, who also is director of the Centre for Shark Research at Mote Marine Laboratory in Sarasota, Florida.

The story of Miss Costa's movements was first reported by the Virginian-Pilot.

Ocearch, the group that tagged Miss Costa, has been doing this since the mid-2000s and has tracked about 300 sharks. The information is used to figure out the "patterns of these animals lives," Hueter said.

"We are trying to identify the important places and times in their life history," he said. "The times they feed, where they feed, where they reproduce and give birth. That then gives us the information we need to protect and sustain them."

The tag typically lasts five years, and Hueter said experts are hoping that Miss Costa will "take us to where she mates".

"And she might show us where she gives birth," he added.

Knowing some of that information, he said, is "necessary and critical for the protection" of the sharks.