Beaches on Cape Cod and Nantucket were peppered by at least a dozen shark sightings Saturday, leading to multiple closures in the late morning and afternoon, authorities said.

On the Cape, shark sightings were confirmed near Coast Guard Beach in Provincetown, Long Nook, High Head, and Ballston beaches in Truro, Marconi Beach in Wellfleet, and Nauset Beach in Orleans in the late morning and afternoon, according to the Atlantic White Shark Conservancy’s Sharktivity app.

Long Nook Beach was closed to swimming from 1:15 to 2:15 p.m., according to the app, citing town officials. Another sighting was listed on the app a short distance away.