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2018–2019 Northeast Pinniped Unusual Mortality Event (CLOSED)

The Unusual Mortality Event affecting stranded gray, harbor, and harp seals between Maine and New York has ended.

New England/Mid-Atlantic

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The Unusual Mortality Event (UME) involving gray, harbor, and harp seals between Maine and New York that began in January 2018 has ended. NOAA Fisheries and partners investigated the event, which occurred from January 1, 2018, through May 31, 2019. 

The UME documented 2,107 stranded seals, including 1,328 harbor seals, 468 gray seals, and 311 harp seals. The investigation determined different drivers impacting the three seal species. The cause of the UME for gray and harbor seals was infection with phocine distemper virus. The cause was undetermined for harp seal strandings, but may have been related to recent population increases and fewer ice-related deaths among the 2018 and 2019 cohort of young harp seals.

Seal Strandings between Maine and New York from January 1, 2018 through May 31, 2019

SpeciesGray SealHarbor SealHarp SealTotal
UME DatesJanuary 1, 2018 - December 31,  2018 May 1, 2018 – December 31,  2018November 28, 2018 - May 31, 2019 
Alive174271142587
Dead2941,0571691,520
Total4681,3283112,107

Harbor and Gray Seals

A bar chart showing annual gray seal strandings, by state, during the 2018-2019 Northeast Pinniped Unusual Mortality Event.
Figure 1: Annual gray seal strandings by state, demonstrating increased strandings of gray seals between Maine and Rhode Island during the 2018-2019 Northeast Pinniped Unusual Mortality Event. Standard deviation is a measure used to quantify the amount of variation within a set of values.

 

A bar chart showing annual harbor seal strandings, by state, during the 2018-2019 Northeast Pinniped Unusual Mortality Event.
Figure 2: Annual harbor seal strandings by state, demonstrating increased strandings of harbor seals between Maine and Rhode Island during the 2018-2019 Northeast Pinniped Unusual Mortality Event. Standard deviation is a measure used to quantify the amount of variation within a set of values.

Harp Seals

 

A bar chart showing annual harp seal strandings, by state, during the 2018-2019 Northeast Pinniped Unusual Mortality Event.
Figure 3: Annual harp seal strandings by state, demonstrating increased strandings of harp seals between New Hampshire and New York during the 2018-2019 Northeast Pinniped Unusual Mortality Event. Standard deviation is a measure used to quantify the amount of variation within a set of values

Partners

We would like to thank the many partners throughout the Northeast who supported this investigation, including:

More Information

Last updated by Office of Protected Resources on 02/04/2026

Unusual Mortality Event National Stranding Network Marine Mammal Health and Stranding Response Program