The dolphin, a 7 foot, 7 inch adult male, received its name due to a missing piece on the trailing edge of its dorsal fin, researchers said.
Big Back Notch was first seen in the region in June 2016. Its last live sighting was on Dec. 23, according to officials.
“It appeared to be active, although a skin condition that had been observed several months earlier had worsened,” a spokesperson for Cascadia Research Collective wrote in a news release.
Researchers said an examination of Big Back Notch was conducted over the weekend and they could not clearly identify a cause of death.
“Preliminary findings include thin (but not emaciated) body condition and no evidence of recent feeding, internal indications of initially coming ashore alive, and a large number of worn, broken and missing teeth that suggest this was likely an older individual,” officials said.
Researchers said the cause of the skin condition is unknown, but said they hope to better understand what happened to Big Back Notch when results of samples collected become available.
Common dolphins typically inhabit warmer waters, but officials said their sightings in the Pacific Northwest have increased over the last 10 to 15 years.
Researchers are interested in tracking the behavior and movements of common dolphins like Big Black Notch and are asking anyone who sees one to contact the Cascadia Research Collective at 360-943-7325.
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