Improved tracking shows for first time that gulf may be home to great white sharks
Posted January 4, 2018 9:56 p.m. EST
Sightings of sharks off Florida coasts are as common as the tides, but not the great white -- or at least, that's what scientists thought before they started tracking the animals.
Three adolescent female great whites -- given the names Katharine, Betsy and most recently, Miss Costa -- have all made the journey to the Gulf of Mexico after they were tagged in New England starting in 2013, suggesting that great whites may be fairly common in these waters.
Miss Costa's tag sent a signal to a satellite tracker while the animal's dorsal fin was above the water's surface Monday off the coast of Tampa Bay. Weighing nearly 1,700 pounds and measuring 12 feet long, Miss Costa got her tag near Massachusetts in fall 2016 and has traveled almost 6,000 miles since.
Great white sharks can circumnavigate the globe 20 times during their lives, but generally stick to their home waters, said Gavin Naylor, director of the shark research program at the University of Florida.
Chet Jennings, a charter fishing captain, has been running tours out of Tampa Bay for more than 20 years and often catches smaller sharks. Jennings has never seen a great white but would love to, despite their reputation as ferocious.
"I wouldn't be afraid," he said. "Unless you were going to try and be aggressive towards it, it's not going to be aggressive towards you."
A fishing party off the St. Lucie Inlet on Florida's east coast made headlines last month when members reported seeing a great white up to 20 feet long. They saw the dorsal fin from about a mile away and figured it must be a giant hammerhead before closing in for the sighting.
Researchers say they're receiving more and more smartphone videos from Florida boaters who have encounters with great white sharks.
The three sharks in the gulf were tracked by the nonprofit research group Ocearch, which follows sharks in real time and shares the data publicly via smartphone app and social media. Ocearch captures and tags marine animals worldwide. The organization has conducted more than 30 research expeditions, including one in 2014 that led to a ban on longline fishing in Ecuador's Galapagos Marine Reserve.
Tagging a shark is a challenge. Sharks must keep swimming at all times or they enter a comalike state called "tonic immobility," Naylor said by phone. The sharks are caught with baited hooks and maneuvered at sea level onto a platform attached to the boat.
The platform rises and scientists get to work, turning the immobile animals on their sides and covering their eyes with a wet cloth to keep them calm as a hose is inserted into their mouths to provide continuous blasts of oxygen.
The whole process takes about 15 minutes, and, according to blood tests, puts the sharks under a minimal amount of stress.
"It's a fairly straightforward process, but one that the casual fisherman shouldn't attempt, because it if goes wrong, it goes wrong in a dramatic way," said Naylor.
Shark tagging emerged in the early 1980s, according to Naylor, when scientist Frank Carey fashioned crude devices with a soldering iron. Another researcher, Jack Casey, came up with a system using orange numbered tags that fishermen along the eastern seaboard would find and send back to him, helping him gather data on where sharks were appearing.
Naylor said the technology used in satellite tags places a shark's movement on a digital map in real time, but it isn't perfect. Much about the animals' life cycle still eludes scientists.
"The tags only transmit information when the shark is at the surface, and they're only at the surface when they're feeding on marine mammals, which are not the majority of their diet," Naylor said.
"So for the huge expanses of time they're eating fish, there are no pings, and the information we gather at the surface can provide a distorted view of the big picture."
It will take decades to find more complete patterns and determine where sharks go during their lives, which can last up to 80 years, Naylor said.
"We need great whites to keep balance in the ocean as top predators," said Dr. Robert Hueter, senior shark scientist at the Mote Marine Laboratory in Sarasota and Ocearch's chief science adviser. "We're trying to find out where they're feeding and reproducing so we know where to focus conservation efforts that will keep the population stable."
Hueter said great whites along the eastern seaboard have traditionally suffered from overfishing, but their numbers are starting to recover.
Naylor and Hueter agreed that the ability to track sharks on social media will encourage the public to champion the animals rather than fear them. With their rows of serrated teeth and a ferocious reputation fed by Hollywood, the great white is not one of the more popular marine creatures.
That may be changing. Many of Ocearch's sharks have thousands of Twitter followers.
"The truth is, white sharks have an important role to play in the oceans," Naylor said. Hueter called these high-on-the-food-chain animals a "needed part of a healthy ecosystem."
Miss Costa was last pinged Tuesday evening, about 80 miles southwest of the mouth of Tampa Bay -- reflecting a sudden turn possibly due to the cold front sweeping through Florida, Hueter said.
Shark watchers can track her path and the path of dozens of other sharks by downloading Ocearch's Global Shark Tracker App for Apple and Android phones or by following Ocearch on Facebook, Twitter, Instagram and YouTube.
Contact Libby Baldwin at firstname.lastname@example.org. Follow her at @LibBaldwin.