Officials in the Cape Cod town of Chatham are asking beachgoers to be careful and not venture too far from shore after a 15-foot-long great white shark was spotted hunting seals in the area this weekend.
More such sightings are likely and while it is rare for deadly predator to attack humans, it can happen, the the town said in a statement posted Monday on its website.
"Use caution when swimming, and you shouldn’t swim around seals," assistant harbormaster Susan Rocanello said this morning.
She said no beach closures had been ordered.
The sighting may only be the beginning of aggressive sharks in the area, Dr. Gregory Skomal, an aquatic biologist with the Massachusetts Division of Marine Fisheries, said Monday.
On Sunday afternoon, spotter pilot George Breen saw the shark in the area of Nauset Beach, approximately two miles north of an inlet, said Chatham harbormaster Stuart Smith.
?It was an aggressive shark that chased some seals?? toward shore, Smith said.
The sighting occurred at around 4 p.m., according to Bill Chaprales, a fisherman who works with Breen on scientific research and spoke with him after the sighting.
Chaprales, who also uses his tuna boat for marine research with the Division of Marine Fisheries, said the shark was said to be around 15 feet long.
"I've been a commercial fisher for over 40 years, and I only saw three until last year," Chaprales said, recalling last summer when he tagged five great whites in two days.
"We think that the higher number of white shark sightings . . . may be related to the growing seal population in that area," Skomal said.
The shark seen Sunday was the second spotted in the region. A 7-foot great white was hooked, tagged, and released on June 26 about 20 miles southeast of Gloucester, prompting a US Coast Guard advisory warning boaters to watch for seals and sharks.
Martin Finucane of the Globe staff contributed to this report.
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