By Lee Roscoe
It’s the mystery surrounding white sharks which attracted a sold out audience to a benefit for Dr. Greg Skomal and the Cape Cod Museum of Natural History. An employee of the Massachusetts Division of Marine Fisheries, Skomal has pioneered shark research in our area since 2009, when they first started chowing down on the rapidly increasing population of grey seals around Monomoy, where he jested, “The café is open.”
Speaking at the museum, Skomal credited the Atlantic White Shark Conservancy with funding his research for the past 2 ½ years. Story went: Cynthia Wigren, its founder asked Dr. Skomal how she could help. “Start a non-profit,” he responded. And she did. It now educates the public, runs a shark camp, hosts the Gill’s Club for girls who love sharks and science.
"The only place in all the huge North Atlantic ocean and its land masses that we can predictably come to to find white sharks, is the Cape,” Skomal said. He's sure that this apex predator has far fewer numbers then do species of fishes at the bottom of the food pyramid. Yet between 1950 and 2010, 200,000 tons were landed, averaging 100 million sharks a year.
“Sharks need a new press agent,” he quipped. Because of “Jaws” and “Sharknado” they engender unwarranted fear. Still, white sharks are no guppies: living to 70, enlarging to 16 feet in length, 13 feet girth, and beyond. They have mammalian qualities, raising their temperature as "warm blooded fish" to above sea-water temperature. As they age their teeth develop and they switch from eating small fish to larger prey such as marine mammals.
“Most of our prior knowledge was from dead sharks which washed up or fishermen brought in,” but reliable ways to study them live were missing until Frank Carey at WHOI invented three dimensional acoustical tagging.
“Technology is constantly evolving,” said Skomal who uses three types of tags. Forty-one great whites have acoustical ones which ping to receivers set in coastal places. “In order to get data, receivers have to be there.” No receivers, no data. He’s tagged 30 whites with pop up satellite tags and also with the help of OCEARCH’s donated vessel, 5 are outfitted with real time satellite tags, constantly sending back data. Acoustical tags cost $400 dollars, sat-tags up to $4,000. In addition he’s worked with WHOI and the Discovery channel who films his adventures, to develop costly underwater drones which can track a shark’s transponder.
Tags help answer many questions including where whites go “spatially and in time.” Many travel up and down the coast from Nova Scotia to Florida. Sharks seem to occur earlier in the summer further north at Truro, descend south as the summer progresses, with the highest concentrations around Orleans and then Chatham around midsummer. By October sharks are migrating through and by November mostly gone. If scientists figure out temperature and other factors affecting occurrence, they could predict where sharks are likely to be.
Skomal’s discovered that many sharks travel to the mid-Atlantic and eastward. These may be females avoiding the violence of breeding areas. Females can delay sperm implantation, giving them an option to become pregnant and come to term out of harm’s way. Tags have also revealed that the more oceanic sharks often dive deep. What they eat at a mid-range of 600 feet down to 3,000 is a mystery.
For population studies, the biologist uses Go-Pro cameras attached to poles and spotter planes to document individuals. Each has a distinctive set of scars and fin shapes. Skomal stressed that numerous shark sightings do not mean high numbers. Hundreds of sightings may occur, but in fact only about 68 animals swim our waters.
On OCEARCH’s website, fans can follow sharks like “Katherine,” (who moves from Monomoy to Cape Cod bay to Falmouth and Nantucket sound) or “Julia,” who, Skomal said, “Always returns to the Cape around Memorial day,” wondering, “Who’s getting her a room?”