CHATHAM – The Atlantic White Shark Conservancy's Sharktivity smartphone app is usually pretty quiet during the winter and early spring months. The white sharks that visit Cape waters during the summer are usually long gone by the new year, and the first sightings of the season usually don't happen until June.
It may have come as a surprise, then, when notifications of shark detections began showing up on the app in January.
Some of those “pings” were after-the-fact detections found when data was downloaded from acoustic receiver buoys from around the Cape and southeastern Massachusetts waters. But others – as recent as April 9 – were nearly real-time and weren't local. The sharks showing up on the app were swimming in Atlantic waters between South Carolina and Florida.
Two white sharks – Hunter and Miss Carolina – were tagged off South Carolina by fisherman Chip Michalove of Outcast Sports Fishing. Miss Carolina was tagged Jan. 20, Hunter on March 9. According to Cynthia Wigren, president of the Atlantic White Shark Conservancy, Dr. Greg Skomal, who has been conducting a shark population study in Cape waters over the past three years, provided Michalove with two Smart Position and Temperature, or SPOT, tags to fasten to the dorsal fins of a couple of great whites. Whenever the sharks break the surface, the tags send a signal to a satellite which is then transmitted to the app.
SPOT tags differ from the acoustic tags that Skomal, senior marine fisheries scientist with the state Division of Marine Fisheries, has attached to sharks here as part of his population study. When a shark with an acoustic tags gets close to a buoy equipped with a receiver, the time, date and individual identity of the shark registers. The data showing those detections, however, has to be downloaded manually from the receiver and then uploaded to the app, whereas the SPOT tags register in real time. Michalove has placed a half dozen acoustic tags on sharks off South Carolina, according to his website.
In a Facebook posting, Skomal said he was “ecstatic” to employ the technology on white sharks in their overwintering grounds in the southeast. “This contributes significantly to our research into the movement ecology of this species, which we started more than a decade ago,” he said. “The ability of Captain Chip Michalove to capture and minimally handle this species off SC is a testament to his skill set.”
Wigren explained that Skomal did not want to use SPOT tags in his Cape population study because attaching them is a more disruptive process than simply jabbing the fish with a harpoon, which is how the acoustic tags are attached. Sharks must be captured so that the SPOT tag can be attached to the dorsal fin, and those sharks then tend to leave the area.
That was the basis of a dispute last year between Skomal and OCEARCH, the research nonprofit that tags sharks around the world. OCEARCH came to Cape waters with its large ship that hoists sharks out of the water to be tagged, tested and sampled. Skomal was concerned those sharks would then leave the area and that would skew the sample population for his study.
Unable to get a permit to operate in state waters, OCEARCH ended up keeping its ship within federal waters, a narrow sliver between Monomoy and Nantucket. They managed to tag several sharks, most of which immediately bolted from the vicinity. Sharks tagged with SPOT tags by OCEARCH can be followed on that organization's Shark Tracker app.
Using SPOT tags on sharks off South Carolina would not have the same impact on Skomal's study, Wigren said. In addition, Michalove was able to tag the sharks without removing them from the water. They were the first sharks off South Carolina to receive SPOT tags.
While the SPOT tags do not register on acoustic receiver buoys, some sharks are outfitted with both kinds of tags, including Miss Carolina and Hunter. There are quite a few acoustic buoys up and down the Carolina coast, Wigren said, which will not only register Miss Carolina and Hunter, but the 85 sharks Skomal has affixed with acoustic tags over the past three years. Again, that data must be manually downloaded, but Wigren said if detections from Massachusetts sharks are found, the information will be communicated to Skomal and added to the Sharktivity app.
Wigren said the population study, funded by the Conservancy, will resume in mid June and continue through the end of October. Skomal was able to obtaining funding for acoustic tags – which cost about $400 – from the state, so the Conservancy will be concentrating its efforts on expanding the array of receiver buoys and raising money to purchase some Pop-off Satellite Archival Tags (PSAT), which cost about $4,000 each. PSATs differ from the acoustic and SPOT tags in that they collect a wide range of data and are programmed to detach from the shark at a specific time, float to the surface and transmit data via satellite.
Skomal used PSATs when he first began tagging sharks off Chatham in 2009, and last summer, working with Warren Joyce, a scientist from the Canadian Department of Fisheries and Oceans, tagged three sharks here with PSATs, said Wigren. The tags were provided by the Canadian government, and Joyce was on board when Skomal attached them to the sharks. The tags are programmed to pop off the animals at a range of times; Skomal said in an email that one popped up off the coast of North Carolina in December, and the other two are scheduled to surface this summer. They will not only provide tracking information and but also data about water temperature and the depths to which the sharks dove. A PSAT that Skomal attached to white shark Curly showed she swam up to 2,500 feet deep in water much colder than researchers expected.
“There are a number of different tags and they all complement the work Greg is doing on the movement of sharks,” Wigren said. Being able to track detections of acoustic tags – by far the most abundantly deployed – in real time is right now the holy grail for local shark researchers. A new real-time receiver will be deployed this season.
An update of the free Sharktivity app to be released within the next few weeks will add the ability to track individual sharks, Wigren said, as well as new icons. The app is available for iPhones and Android devices, and has been downloaded more than 100,000 times.
Since Skomal's study began in 2014, a total of 257 individual great white sharks have been identified in the waters from Truro to Chatham, with the largest concentration off Monomoy, which also, not surprisingly, has the highest population of gray seals in the area.