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14‑Foot Thresher Shark Dies After Stranding Off Wellfleet During Migration

A 14‑foot thresher shark stranded in shallow water off Mayo Beach in Wellfleet, Massachusetts, and died before volunteer rescuers arrived. Photos showed a slender shark with a long, whip‑like tail and visible injuries. NECWA said the animal was in poor condition and a necropsy was performed. Strandings of migrating threshers are common on Cape Cod in cooler months, when falling bay temperatures (below about 50°F) can cause cold‑stunning.

03:53 PM, 12/04/2025Environment
14‑Foot Thresher Shark Dies After Stranding Off Wellfleet During Migration

A 14‑foot thresher shark was found stranded in shallow water off Mayo Beach in Wellfleet, Massachusetts, and died shortly before volunteer rescuers arrived.

What happened

The New England Coastal Wildlife Alliance (NECWA) received multiple reports of a possibly live thresher shark in the shallows and rushed to the scene, but responders were unable to reach the animal before it died. Photographs from the site show the long, slender shark with its characteristic whip‑like tail — roughly half the length of its body — and visible, track‑like injuries along its flanks.

Condition and investigation

NECWA reported the shark was in poor condition by the time rescuers arrived. A necropsy was performed to help determine the cause of death. Shark biologist John Chisholm was contacted for further information about the postmortem findings.

“The fish that died in Wellfleet was alive when first sighted but was not in great shape,” said Krill Carson, marine biologist and president of NECWA, noting that responders arrived too late to save the animal.

Why these strandings happen

Thresher shark strandings are relatively common along Cape Cod during the colder months. NECWA explained that many threshers are migrating south in the fall and can become trapped in Cape Cod’s inner harbors and bays. Once confined in shallow or enclosed waters, these sharks face a heightened risk because they tolerate cold poorly.

At the time of this incident, bay water temperatures were below about 50°F and continuing to drop — conditions that can lead to cold‑stunning or cold‑shock. “A handful of threshers strand each season as they get trapped inside Cape Cod and are unable to continue their migration south,” Carson added.

About NECWA

NECWA is an all‑volunteer organization that responds to marine wildlife strandings and conducts research. The group accepts donations to support response and research efforts through necwa.org.

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