Authorities in Chatham have banned swimming on east-facing oceanside beaches after more reports of great white sharks in the vicinity, including sightings of a shark killing a seal close to the beach.
The closures include North Beach, North Beach Island, and South Beach, the town harbormaster’s office said in a statement issued Monday afternoon.
“This updated closure is based on credible sightings over the weekend of shark activity close to the shoreline near the south end of North Beach,’’ the statement said.
Chatham Parks and Recreation Director Dan Tobin said visitors to North Beach Island and harbormaster staff had seen a great white shark attack and kill a seal close to shore.
“It was eaten by the shark,’’ he said. He said that although not many shark sightings had been reported over the weekend, “the proximity off the beach’’ prompted town officials to close the area.
Swimming at Lighthouse Beach is still banned from 5 p.m. to 9:30 a.m. daily and swimming remains banned when seals — a favorite food of the fearsome great whites — are within 300 feet. Tobin said Lighthouse Beach, a popular destination, remains open during the day because staff are able to patrol the water during those hours.
“Beach goers, mariners and swimmers should continue to pay close attention to their surroundings, and when swimming at Lighthouse Beach should not venture too far from shore,’’ the statement said.
Swimming is still allowed on south side beaches in Nantucket Sound and in all other areas, the notice to swimmers said.
Gregory Skomal, a state marine biologist, said he has not seen an increase in shark activity over the past few days, although a spotter plane pilot working for the state reported seeing great whites off Chatham on Aug. 9 and Aug. 12.
Shark sightings so far this summer have topped 35, he said, about the same as the number of sightings reported at this time last summer. But the number of sightings is not a reliable indicator of the number of sharks in the area, since the same shark may be spotted multiple times, he said.