An ‘unusual mortality event’ leaves 30 whales dead in Alaska, scientists baffled

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A fin whale carcass found on Whale Island, Alaska in the Kodiak Archipelago in June, 2015.

Scientists are scratching their heads over the death of 30 large whales during the past few months off the coasts of Alaska, in what NOAA is calling an “unusual mortality event.”

A fin whale carcass is surrounded by bears in Larson Bay, Alaska, June 13, 2015. Photo: NOAA.

A fin whale carcass is surrounded by bears in Larson Bay, Alaska, June 13, 2015. Photo: NOAA.

Since May, 11 fin whales, 14 humpback whales, one gray whale, and four other unidentified cetaceans have stranded around the islands of the western Gulf of Alaska and the southern shoreline of the Alaska Peninsula.

This is three times the typical number of large whale strandings.





The National Oceanic and Atmospheric Administration announced last week that it is planning a more intense investigation into what is causing the die-off. Labeling it an “unusual mortality event” allows it access to additional resources in its investigation. According to NOAA, an UME is an “unexpected… significant die-off of a marine mammal population.”

However, the organization said that the data collection and analysis could take years to complete for the investigation.

Whale stranding deaths by year

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“NOAA Fisheries scientists and partners are very concerned about the large number of whales stranding in the western Gulf of Alaska in recent months,” NOAA’s Dr. Teri Rowles said in a statement. “While we do not yet know the cause of these strandings, our investigations will give us important information on the health of whales and the ecosystems where they live.”


Researchers have run tests to determine if toxins could have been involved, but the results are so far inconclusive, Rowles told Alaska Public Radio. She added that they needed more samples from the dead whales to do further testing, but that getting them is no small feat.

“Trying to investigate large whale mortality events provides a lot of logistical complications and getting access to good samples, getting access safely to carcasses, and even finding a place for carcasses to be towed and examined,” she said.

Outside the U.S., NOAA reported that colleagues in Canada reported six dead stranded large whales. Between August 7 and 13, four humpbacks and one sperm whale were reported dead in British Columbia and two have been necropsied.

“Our leading theory at this point is that the harmful algal bloom has contributed to the deaths,” NOAA spokesperson Julie Speegle told the Guardian. “But we have no conclusive evidence. The bottom line is we don’t know what’s causing these deaths.”

Other recent Unusual Mortality Events as noted by NOAA:

  • 2013: Bottlenose Dolphins in the mid-Atlantic
  • 2013: Bottlenose Dolphins in Florida
  • 2013: California Sea Lions
  • 2011-2012: Bottlenose Dolphins in Texas
  • 2011: Northern Alaska Pinnipeds
  • 2011: Northeast Pinnipeds
  • 2010-2014: Northern Gulf of Mexico Cetaceans