In what is believed to be driven by climate change and increasing water temperatures, marine biologists are reporting a steady increase in the presence of smooth hammerhead sharks in Vineyard and New England waters in the past several years.
The recent trend was supported by the sighting of a half-dozen hammerheads off Cuttyhunk Island on July 13, reported by multiple fishermen. Similar sightings of the species were also made on the south side of the Vineyard and Nantucket, days prior. And on Tuesday, Falmouth town officials reported that a hammerhead was likely spotted off Surf Drive.
“The expectation is that we will start to see more and more of smooth hammerheads,” said John Chisholm, adjunct scientist with the New England Aquarium Anderson Cabot Center for Ocean Life. “We’ve been keeping track of the numbers and reports, and we can see every year, especially the past three years, [that] from July to early September we’re getting more and more sightings.”
Chisholm worked alongside Massachusetts shark expert Greg Skomal for decades before joining the aquarium. Skomal, who has been studying sharks for more than 50 years, has also noted an increase in hammerhead sightings in Vineyard waters.
“The reports are certainly increasing, and could very well be a function of warming waters,” Skomal told The Times. Historically, researchers dating back to the 1950s and earlier reported that the species would rarely travel to northern waters, and they considered them strays: “We are seeing them a little more consistently in Southern New England.”
There are many different hammerhead species; likely the most famous are great hammerheads, which are more dangerous. Smooth hammerheads can still reach lengths of 12 feet, and typically reside in tropical waters, though they have been spotted as far north as Nova Scotia.
Chisholm also believes the rise in local sightings has coincided with the increase in water temperatures, noting that other species, like blacktip sharks, spinner sharks, and even bull sharks have been reported farther and farther north. A bull shark was seen in Montauk last year.
“Our water hasn’t been warm enough, but now it is in their comfort zone, and they are expanding north,” Chisholm said of hammerheads, noting that the Vineyard will “absolutely” start to see more of them.
There are questions that Chisholm and other scientists have about the species, and he’s hopeful they will start a tagging program in the near future to gain a better understanding.
As for beach safety around hammerheads, the message from Skomal and Chisholm is to not be alarmed. The species is not nearly as dangerous as its counterpart, the white shark. Neither has heard of a fatality from a hammerhead, as they aren’t aggressive, nor interested in humans. Hammerheads typically feed on smaller fish and squid, even crab and lobster. White sharks typically make a mistake when attacking a human, thinking they may be a seal. Hunting for small species minimizes that change.
Still, hammerheads are large predators and have sharp teeth, and Chisholm said that beachgoers should take protective measures when they come close to shore, which they are known to do. If in proximity to a hammerhead, he suggests, get to a safe space, which is either out of the water completely or less than knee-deep, noting that they will usually move out of the area pretty quickly. ”Treat it with respect,” he said.
Skomal echoed Chisolm’s statements not to fret. “People shouldn’t be alarmed. It could be a function of climate change, which could be alarming,” Skomal said. “But don’t be alarmed relative to your safety and the species.”
As to how the public can help researchers get a better understanding of the species, Chisholm asks that any fishermen or beachgoer report a hammerhead sighting.
“We depend on sightings from fishermen and the public,” he said. “Every sighting is a data point.” Send Chisholm an email at masssharks@gmail.com if spotting a shark, or find him on social media by his Instagram handle, @ma_sharks.