A closer look at whale deaths

Fri, 10/13/2017 - 8:45am
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The unusual die-off of humpback whales along the east coast is the 63rd out of 64 unusual mortality events that the National Oceanic and Atmospheric Administration has declared since 1991.

According to information provided online by NOAA, an unusual mortality event is defined under the Marine Mammal Protection Act as "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response."

NOAA currently has six active UMEs, one of which dates back to 2011 (for northern Alaska pinnipeds), and also includes California sea lions, large whales in Alaska, Guadalupe fur seals in California, the North Atlantic right whales (declared in 2017), and the humpback whales in the Atlantic (2016). There were previously two UMEs called for humpback whales: one in 2003 (which saw other large whales die in the Gulf of Maine), and in 2006 in the North Atlantic, the cause of which is still undetermined.

The NOAA Fisheries UME page on its website shows that the following humpback whale deaths were recorded in the following states in 2016:

Delaware (3); Massachusetts (3); Maryland (1); Maine (2); North Carolina (5); New Hampshire (1); New Jersey (2); New York (4); Rhode Island (1) and Virginia (3).

The following statistics have been recorded for the period ending on Sept. 30, 2017 (and therefore would not include the humpback whale discovered on Ballard’s Beach on Oct. 1):

Delaware (2); Massachusetts (6); Maryland (1); Maine (0); North Carolina (6); New Hampshire (0); New Jersey (3); New York (1); Rhode Island (2); Virginia (6).

As to why the whales are stranding, the NOAA website states, “A portion of the whales have shown evidence of pre-mortem vessel strike; however, this finding is not consistent across all of the whales examined so more research is needed. As part of the UME investigation process, an independent team of scientists (Investigative Team) is being assembled to coordinate with the Working Group on Marine Mammal Unusual Mortality Events to review the data collected, sample future whales that strand and to determine the next steps for the investigation.”

In a frequently asked question page on the NOAA website, the question as to test findings is answered this way: 

“Many of the carcasses have been in states of advanced decomposition or floating and not been retrievable. However, partial or full necropsy examinations were conducted on approximately half of the 42 cases that occurred through April 2017. Of the 20 cases examined through April, 10 cases had evidence of blunt force trauma or pre-mortem propeller wounds indicative of vessel strike, which is over six times above the 16-year average of 1.5 whales showing signs of vessel strike in this region. Vessel strikes were documented for stranded humpback whales in Virginia (3), New York (3), Delaware (2), Massachusetts (1) and New Hampshire (1).”

According to NOAA, the states with the most declared UMEs are Florida and California.

A humpback whale was discovered washed ashore on Block Island on either Oct. 1 or Oct. 2 at Ballard’s Beach. A team from Mystic Aquarium arrived on Block Island four days later to perform a necropsy. 

Before the testing began, the whale was dragged to nearby property owned by The Land Trust, where the whale was buried after the test samples had been taken. (Another humpback was found at Mohegan Bluffs in early September, and test samples were also taken from that whale.)

A spokesperson for the National Oceanic and Atmospheric Administration said the test results could take months. NOAA has declared an “unusual mortality event” for whales due to the unusual numbers that have died since April 2016. 
According to NOAA, “The best estimates for the numbers of humpback whales that reside in the North Atlantic Ocean, including U.S. Atlantic coastal waters, is 10,400-10,752 animals, based upon an international collaboration in 1992-1993 to study North Atlantic humpback whales across their known range...”