CHATHAM – If a picture is worth 1,000 words, shark researchers have found that a video can answer 1,000 questions.
Conservation of Atlantic white sharks Scientist Megan Winton was examining footage from first year of video tagging when she came across a new tag great White shark who had just eaten a seal – telltale sign: seal intestines hanging from its gills – and was resting on the ocean floor.
Winton was initially disappointed that they missed the actual predation, something they rarely saw, but was fascinated to witness the rather unusual behavior of a shark lying down after eating. to rest and digest. The instruments on board the beacon confirmed what they were witnessing, that the large animal was not moving and had pointed into the current so that oxygen-rich water could flow over its gills.
âThe overall objective (of the project funded by the grant) was to characterize predatory behavior,â Winton said. But this resting behavior was something entirely unexpected. She said her mind started running to other datasets collected during conventional acoustic tagging and adding this observed behavior to explain some of the anomalies and unknowns.
It’s like looking over their shoulder as they do what sharks do. Although there are occasional attacks on a seal or fruit bat, most of the time they are just sailing, looking for the next meal.
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âWe actually don’t spend a lot of time watching what sharks are doing,â Winton said. “It makes me very happy to be a scientist right now because (the technology) is going to keep getting better.”
In 2019, the conservatory and National Marine Fisheries Division shark researcher Gregory Skomal used a grant from Save Our Seas Foundation to buy two video tags. Costing around $ 10,000 each, the tags are the size of a soccer ball, look like a hot pink version of the Goldfish cracker, and are attached to a great white shark by a thin steel cable attached to a surgical steel tip. integrated into the base of a shark. dorsal fin using a harpoon.
This is the same method Skomal has used for years to affix acoustic labels to hundreds of great whites.
Since the Atlantic White Shark Conservancy began funding the effort in 2013, Skomal, working with volunteers and conservation staff, has tagged 250 white sharks. During the last tagging season, which runs from spring to late fall, they acoustically tagged 39 sharks.
Skomal also attached the new video beacons to 10 of these sharks in 2021. While the acoustic beacons only broadcast a unique identifying signal picked up by coastal receivers mounted on buoys all along the Cape Coast and the Atlantic, the video beacon does much more than film the shark.
These pink soccer balls contain an accelerometer that can measure and record changes in speed and a gyroscope that can discern the orientation of the body – whether a shark dives to sting or sting, for example.
Other instruments record location, depth, water temperature and light. It’s like a Fitbit for sharks, Winton said.
In total, the beacon records one million data points, including 11 hours of video and 48 to 72 hours of information from other instruments before the cable is automatically severed and the beacon floats on the surface. It’s a wealth of information, but it has a downside.
Just as they did with the video information they record using underwater cameras on long poles, which help the Skomal team identify the sharks they encounter, the sheer volume of data from video tags needs to be processed, captured and analyzed.
The processing of video data taken during the five-year tagging portion of the Winton White Shark Population Study, completed in 2018, has been the biggest obstacle to the completion and publication of the study.
âWe have our work cut out for us this winter,â Winton said. “This is how it goes.”
But the first project to undertake now that the tagging season is over is the completion of a Woods Hole Sea Grant-Funded study that combines tagging data with environmental data to see how conditions such as water temperature, currents, and water clarity affect a shark’s presence in a certain location. This analysis will be used to build a predictive model that could help inform water users about when a shark is most likely to be at a specific beach.
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Next is the completion of the long-awaited five-year demographic study that attempts to quantify the number of great whites that come to Cape waters – and perhaps a hint of the larger population of white sharks.
Winton said the research Conservation of Atlantic white sharks and Skomal involves collaborative studies with scientists from elsewhere.
âA lot of people don’t realize that our work here informs research across the region,â Winton said.
The other problem with video tags, known as CATS tags (the company name is Customized animal tracking solutions), is that they must be retrieved for the information to be downloaded. Sometime after the camera’s memory is full, the beacon breaks the tether, floats on the surface, and broadcasts a locator signal via satellite.
Sharks can travel, and although most of the tags were collected from local waters, last summer Winton and Skomal had to travel to Rockland, Maine and hitchhike on a mail boat to retrieve some. a. Recovery is important not only because of the data they contain, but also because these expensive little soccer balls are used over and over again.
The Skomal team lost one during the great northeast which hit the Cape region at the end of October. It appeared in bad weather and was blown southwest, struck the Gulf Stream and vanished, Winton said.
âWe hope someone finds him on the beach in Portugal,â she said.