Posted on 06/30/2021 10:04:29 AM PDT by Capt. Tom
CHATHAM — The annual summer preview, with shark researchers debriefing the media of the prior year and a look ahead to research being conducted this year, didn’t have many surprises.
It’s become a fact of life for residents and visitors that hundreds, if not more, great white sharks will be hunting seals along Cape beaches in close proximity to humans.
What the briefing Tuesday morning at the Atlantic White Shark Conservancy’s Chatham Shark Center did reveal was a tantalizing look at the potential of various research projects to peer into the daily life of these apex predators — and how that could pay off with enhanced public safety. “We are hoping to find patterns that lead to predictability, and ultimately, forecasting,” said state Division of Marine Fisheries shark researcher Greg Skomal.
A population study by Skomal and shark conservancy scientist Megan Winton will not be published this summer but it has identified 407 sharks over a five-year period from 2014-2019. Seasonal broad-scale movements are emerging from the more than 179 sharks still carrying active acoustic tags that emit a unique identifying signal; the more than 100 receivers nearly encircling the Cape and along the South Shore capable of detecting, identifying and logging that signal; and the realtime receivers at major beaches from Truro to Chatham.
“A lot of this is tightly linked to water temperature,” said Skomal.
The water is still cool in June and detections are slow. As the water warms, July arrivals tick up, but are still relatively sparse with an average of 2,500 detections. August is high season with around 15,000 detections, with October nearly as busy, followed by a sharp drop-off in November as the ocean cools off. With the exception of a few stragglers, great whites are gone by December, 10 years of tagging data showed.
With funding from Woods Hole Sea Grant, Winton hired a post-doctoral researcher to look for patterns in overlaying a decade of tagging data onto environmental conditions to build a forecast model showing how water temperature, time of day, currents and turbidity may help predict where sharks are more likely to be present.
But it’s not so much arrivals and departures, but what the predators do while they are here that really interests shark researchers and those tasked with public safety on Cape beaches. At Tuesday’s preview, Skomal and Winton revealed research into shark behavior that seeks to marry environmental data with behavioral observations by sophisticated tags, specialized grids of receivers, aerial photography and videos and discrete study areas.
State Division of Marine Fisheries shark researcher Greg Skomal talks about recent shark research Tuesday at a press conference at the Atlantic White Shark Conservancy's Shark Center in Chatham.
Skomal explains how a pair of acoustic buoys can transmit real-time data to shore from tagged great white sharks. He deployed the buoys Tuesday, one at Head of the Meadow Beach in Truro and the other at Newcomb Hollow Beach in Welfleet. A population study by Skomal and shark conservancy scientist Megan Winton has identified 407 sharks over a five-year period.
Data from a satellite tag that collected position, water temperature and depth for 30 days in 2019 revealed that sharks spent about half their time in depths shallower than 15 feet. That also happens to be where people spend a lot of their time in the ocean and the bulk of the research investigates why and how great white sharks hunt in those shallow waters.
Skomal said researchers assume that a great white swimming in shallow water is there to feed.
“These are big animals; they don’t like tides or currents. They don’t like shallow water, sandbars and shoaling. They are coming in, taking a risk because there is a big energetic payoff (a seal),” said Skomal.
Working with the Center for Coastal Studies in Provincetown, University of Massachusetts doctoral candidate Brian Legare will again set up over 50 acoustic receivers in a grid formation at Head of the Meadow Beach in Truro and Nauset Beach in Orleans. As a tagged shark swims through the array of receivers, its position is determined by triangulating signal strength between multiple receivers.
“Think of it as an E-ZPass system for sharks,” Winton said.
That position is overlaid on a map of bottom features like sandbars. Some sharks will be carrying tags that can detect and record the acceleration and body posture of the shark. Other tags have video cameras attached to the base of the large triangular dorsal fin that record what the shark is seeing and environmental data like water depth and temperature.
Skomal said researchers will be flying a dirigible shaped balloon equipped with sophisticated camera technology to reveal a visual record of shark movements that corresponds to what is being recorded on the tags.
“This is a very sophisticated game of cat-and mouse,” Skomal said. “(I)t’s a bit of a chess game and we are trying to figure out exactly how it plays out.”
While researchers rarely witness these predations, Skomal and Winton described the unsuccessful attack on a seal in October 2019 by a shark named Chopper that was documented by spotter pilot Wayne Davis, and by video and accelerometer tags. Twenty times a minute, the accelerometer tag records the tail beat of the great white, as well as depth and other environmental data.
The video feed is like looking over the shoulder of the shark as it pursues the seal. The accelerometer showed a rapid acceleration into shallow water, as the video revealed the shark working hard in pursuit of the seal that could be glimpsed briefly under the right pectoral fin.
Researchers combined the tag data with bottom contour mapping and produced an animated recreation of the attack on the seal.
“How frequently do sharks attempt to kill seals? What role do the weather and oceanographic conditions play? All that we can get from tags,” said Skomal.
By the number of beach closures, shark sightings and predatory events witnessed by beachgoers, it is a game whose playing field is perilously close to people.
There have been four recent great white shark attacks on Cape Cod, including a fatal attack on bodyboarder Arthur Medici in Wellfleet in September 2018. Two kayakers were attacked in Plymouth in 2014 and Maine had its first fatal attack last summer.
The fine-scale research conducted by Legare has already produced interesting results, with 31 tagged sharks swimming through the Head of the Meadow grid from Sept. 15 to Oct. 5, 2019.
“We found the sharks spend a lot of time in the trough between two sandbars,” said Skomal. “If you are managing a beach, or lifeguarding and you know a little about the …bathymetry of your area, you might be able to get a sense, based on the data we’re collecting here thanks to Brian’s (Legare) research of what areas might be more vulnerable to the presence of these animals.”
The white sharks now will be in all new England waters and should be regularly be sighted, and ping all the hydrophone buoys being placed here in the ocean.
And this will continue in New England, until December, when the shark hydrophone buoys are pulled out, to avoid the winter storms.-Tom
White sharks are racist....................
There’s so much we can learn from sharks.
Their work on the Covid vaccine is genius.
Fins to the left, fins to the right...
And you’re the only bait in town.
We need a bigger boat.
Quick!
Man-eater!
That was the common name used for centuries to describe the shark species, Carcharodon carcharias.
From the 1975 movie "JAWS": Mayor Vaughn: "And what did you say the name of this shark is?" Hooper: "It's a Carcharodon carcharias. It's a Great White."
The 1975 Movie JAWS made the words "great white" and “white shark” popular with the public, and “man-eater” is rarely used today. That common word change from "man-eater" to "great white" or "white shark," helped in getting Carcharodon carcharias to become a protected species. It’s a lot easier to get support to protect a “white shark,” than it would be to protect a “man-eater”.
The other common names used to describe this species such as “white shark," “white pointer,” “great white shark" and “white death,” seems to have come into popular usage because Carcharodon carcharias shows so much white on the belly and sides. The white on the sides abruptly changes to the topside color without the usual transitional area seen on many other shark species.-Tom
Lawyers are safe.....Professional Courtesy
Great minds..
Yes, all of us.
Watch out boy, she’ll chew you up...
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