‘Shark Party’ Off Block Island: Aerial Survey Spots ~400 Spinner Sharks — Could Warming Waters Be Shifting Their Range?

About 400 spinner sharks filmed in a tight school south of Block Island

Aerial observers from the Rhode Island Department of Environmental Management (DEM) and the Anderson Cabot Center for Ocean Life at the New England Aquarium photographed an estimated 400 spinner sharks roughly 10 miles south of Block Island during an August survey conducted while tracking North Atlantic right whales.

"Talk about a party," the DEM wrote when sharing the images. The team said the aggregation initially appeared small from the air, but after circling the area they realized the group could number in the hundreds. Sonja Feinberg, an aerial observer with the Anderson Cabot Center, said, "I was very surprised because I have never seen an aggregation that large."

"This is our first time seeing a tight-knit aggregation of spinner sharks of this size," said Orla O'Brien, research scientist and leader of the aerial survey team. The only other comparably large aggregation the group has documented was a congregation of more than 1,000 basking sharks in November 2013.

The researchers used high-resolution aerial images to identify the animals by morphological features such as fin shape and body proportions, and by noting their tendency to travel in groups. The DEM acknowledged that sandbar sharks — another schooling species increasingly observed locally — remain a possibility, but scientists are "leaning more toward" spinner sharks as the best match.

Young shark and possible northward nursery shift

Spinner sharks are typically associated with warmer waters from Florida to the Carolinas, but warming ocean temperatures are bringing subtropical species farther north. On Sept. 1, 2024, local fisherman Capt. Carl Granquist captured video of a 24-inch spinner shark just south of Charlestown. The juvenile exhibited a partially healed umbilical scar, indicating it was a young-of-the-year.

That specimen prompted scientists to ask whether juvenile spinner sharks are migrating unusually far north or whether nursery habitat may be shifting poleward. The finding led to a paper in the Journal of Fish Biology by Joshua Moyer (Atlantic Shark Institute), Jon Dodd (Atlantic Shark Institute), and Stephen Kajiura (Florida Atlantic University). Dodd called a potential birth in Rhode Island "unique" and said it raises new questions about spinner shark distribution.

Behavior, size and safety

The Florida Museum of Natural History describes spinner sharks as slender, gray-bronze sharks named for their dramatic aerial spinning behavior: while feeding they may swim through baitfish schools, spin along their axis, and breach the surface — sometimes as high as 20 feet — snapping at prey. Spinner sharks average about 6.4 feet in length.

According to the museum's International Shark Attack File, spinner sharks have been linked to 16 unprovoked attacks on humans, none fatal; their teeth are adapted for seizing small fish, so bites typically cause relatively minor injuries.

Other marine life seen during the survey

The DEM also reported observing three minke whales, 14 fin whales and one humpback whale during the same August aerial survey. It is unclear whether the sharks and whales were close to one another; the DEM emphasized spinner sharks primarily forage on fish and are not whale predators.

What this means: The unusually large aggregation and the juvenile spinner sighting farther north both add to evidence that subtropical shark species are appearing more often in New England waters. Scientists caution that further study is needed to determine whether spinner sharks are establishing northern nurseries or simply expanding seasonal ranges in response to warming seas.