BAR HARBOR — The number of minke whales found by stranding networks between Maine and South Carolina in 2017 was more than twice the normal average, prompting the National Oceanic and Atmospheric Administration to declare an unusual mortality event (UME) for the species.
The declaration is in response to information collected from Jan. 2017 to Jan. 2018. NOAA coordinates a network of stranding-response organizations; Allied Whale at College of the Atlantic is a member of the network. Stranding-response groups responded to 29 minke whale strandings during the year, more than double than the average 12 strandings per year.
Minke whales are protected under the Marine Mammal Protection Act, but the species is not listed as endangered or threatened under the Endangered Species Act. Population estimates for minke whales in the region range from 1,425 to 2,500 animals, according to a 2011 shipboard and aerial survey.
Of the 29 stranded minke whales, 19 were found dead, and 10 were alive, but only one whale ultimately survived. Eighteen had partial or complete necropsies, six only had documentation (photos and measurements), and five were not recovered or examined.
One of those necropsies was conducted on MDI by Allied Whale in August. The whale was towed to Seal Cove after it was found floating dead in Blue Hill Bay. A week earlier, the Maine Marine Patrol had disentangled another minke from fishing gear near the entrance to Frenchman Bay.
“We’re having to deal with three unusual mortality events of large whales,” said Teri Rowles, Marine Mammal Health and Stranding Program coordinator at the NOAA Fisheries Office of Protected Resources in a media teleconference Jan. 30, referring to UMEs also declared for humpback and North Atlantic right whales.
No direct connection has been found between the three UMEs, and no single cause has been identified, but scientists hope an investigation can clarify any commonalities in the findings from the three species.
This is a “fairly robust task” for the stranding networks along the Atlantic coast, Rowles said. For that reason, NOAA plans to integrate the response to the three events as much as possible so that the networks have clear guidance on what data they should be collecting for each of these species and investigations. The agency also will assist with moving personnel, vessels or aerial support to the local stranding networks.
Eight strandings were reported in Massachusetts. Seven happened in New York, which also had the highest increase over historic averages of any of the coastal states. Six strandings were recorded in Maine.
Of the 24 animals that were documented, 11 had suspected or confirmed evidence of human interaction, nine due to fishery interactions and two with blunt-force trauma. Eight whales showed evidence of infectious disease.
In addition, NOAA is assembling an independent team of scientists who, in cooperation with the Working Group on Marine Mammal Unusual Mortality Events, will review data collected, sample stranded whales and determine how to advance the investigation process.
UMEs involving minke whales occurred twice before, in 2003 and 2005. The 2003 event was in Maine, and involved 22 minke whales. No definitive cause was found, but approximately 41 percent of the whales showed evidence of fisheries interaction, according to NOAA.
The 2005 UME was a multispecies large whale event that ranged from Maine to Maryland. It involved only 10 minke whales, and in this case as well, no definitive cause was determined.
“We really encourage rapid reporting so that we can investigate the cause of the mortality and retrieve the carcass if possible, or if it’s a live whale, we can render aid,” said Rowles.