A young female bottlenose dolphin, discovered dead on the shore of Fire Island on Tuesday morning, showed signs of chronic disease in a necropsy done to determine why she died, a conservation society said.

The 5- to 6-foot dolphin washed up between Fair Harbor and Saltaire, and was reported by a member of the public at about 7 a.m., the Atlantic Marine Conservation Society said in a statement.

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The society’s biologists, assisted by the Fire Island National Seashore and Suffolk County Water Authority, determined the dolphin was 3 to 5 years old, and likely had died within 24 hours of being found.

It will take several weeks for a pathologist to review samples to try to identify any specific ailments that might have killed her, the statement said.