Frequent Questions: 2018-2019 Ice Seal Unusual Mortality Event

Why was the Unusual Mortality Event Closed?

The increased stranding rate that triggered the Unusual Mortality Event declaration is no longer occurring. Strandings returned to baseline levels during 2020 and 2021.

How widespread was this Unusual Mortality Event?

Based on the Alaska stranding data, the 2018-2019 UME was located in the northern Bering Sea (north of 60 degrees) and eastern Chukchi Sea and spanned between Utqiaġvik to Kotlik and west to Saint Lawrence Island.

What were the dates for this Unusual Mortality Event? How many seals, and which age classes, were included?

The Unusual Mortality Event occurred from June 1, 2018 through December 31, 2019 with peak strandings between June 1, 2018 and August 31, 2019. There were 284 ice seal strandings, including 97 bearded seals, 75 ringed seals, 48 spotted seals, and 64 seals of unidentified species. Although the stranded ice seals were all age classes (pup, yearling, sub-adult, and adult), most stranded seals were young seals. Of the 284 stranded seals, only 32 seals were adult seals.

What do scientists believe is the most likely cause of this Unusual Mortality Event?

The preliminary cause of this UME was due to the changes in the marine ecosystem resulting from unprecedented ocean warming in the northern Bering Sea during the winters of 2017-2018 and 2018-2019. The warming ocean created prey availability changes and thus reduced the ecosystem’s carrying capacity leading to the poor nutritional condition and increased mortality in the seals documented during the UME. There were concurrent seabird mortality events—and a Unusual Mortality Event for eastern North Pacific gray whales—in the same area linked to malnutrition. 

Beginning in 2017, NOAA documented an unparalleled increase of large-bodied, predatory, commercially viable fish—such as Walleye pollock (Gadus chalcogrammus) and Pacific cod (Gadus macrocephalus)—in the northern Bering Sea. This coincided with an extraordinary decline in the biomass of small-bodied, fatty, forage fish in the northern Bering Sea—such as Arctic cod (Boreogadus saida) and capelin (Mallotus villosus)—which are known to be nutritionally important to ice seals.

Did the Unusual Mortality Event have public health or subsistence harvest implications?

The increased mortality of ice seals documented during 2018-2019 was a direct food safety, food security, and conservation concern to all coastal peoples of the Bering Sea and Chukchi Sea. No direct public health factors were associated with the ice seal UME. 

Some harvested seals were reported in poor body condition during this UME.

Did climate change contribute to the Unusual Mortality Event?

Regional warming events in 2017 and 2018 contributed to the poor nutritional condition of ice seals, and it is clear that warming waters and the subsequent reduction in sea ice played a role. Exceptional regional ecosystem-level effects due to warm waters reduced the quality, quantity, and extent of the sea ice in the Bering Sea during winter and summer 2018 and 2019. These temperatures created unprecedented warm environmental conditions that caused an extraordinary ecological shift in the marine ecosystem. This resulted in the southeastern Bering Sea ecosystem beginning to rapidly move north, which led to an unprecedented reduction in the carrying capacity of the ecosystem to provide the necessary foods to the number of seals via reduced prey availability. This event occurred in the Alaskan waters of the northern Bering Sea during the critical spring seal pupping, nursing, breeding, and molting season. 

Were other mammals or animals affected by this die-off event?

Changes in forage fish, seabirds, and snow crabs were documented in the Bering Sea. Since 2015, capelin and other forage fish have decreased greatly in abundance. For capelin, the 2018-2021 biomass estimates and frequency of occurrence are by far the lowest in the time series and it seems that capelin have largely disappeared from the ecosystem. Since 2015, thousands of seabirds of multiple species have died annually due to malnutrition in the northern Bering Sea. Since 2018, more than 10 billion snow crabs have disappeared from the eastern Bering Sea, and the population collapsed to historical lows in 2021. The collapse is linked to the marine heatwave in the eastern Bering Sea during 2018 and 2019.

What is next now that the Unusual Mortality Event has been closed?

The Alaska Marine Mammal Stranding Network will continue to respond to reports of live and dead stranded ice seals and sample the animals when feasible. We will continue to consult with the Ice Seal Committee on ice seal health conditions of harvested seals.

How many ice seal Unusual Mortality Events have previously occurred in Alaska?

One previous Unusual Mortality Event involving all four species of ice seals in the Bering Sea and Chukchi Sea occurred between 2011 and 2016. The minimum estimate of impacted seals in Alaskan waters for that event was 657. The investigation identified seals with clinical signs consistent with an abnormality of the molt, including fluid filled circular skin lesions, as well as some lethargic seals, but a definitive cause for the UME was not determined. 

Where can I find additional information on ice seals and other Unusual Mortality Events?

Visit our website to find more information on bearded seals, ringed seals, and spotted seals, and other Unusual Mortality Events.

What should people do if they find stranded or distressed marine mammals?

In Alaska, report all dead, injured, or distressed marine mammals to NOAA’s 24-hour stranding hotline at 1-877-925-7773. Or contact the local stranding network.

What should people do if they witness harassment or any marine mammal violation in the water or on the beach?

All marine mammals are federally protected under the Marine Mammal Protection Act (MMPA). Only local and state officials and people authorized by NOAA Fisheries may legally handle live and dead marine mammals. However, MMPA exempts Alaska Native takes of marine mammals for subsistence purposes or for the purpose of creating and selling authentic native articles of handicrafts and clothing, provided it is not done in a wasteful manner (16 U.S.C. 1371(b)). To report case violations, please contact NOAA’s Office of Law Enforcement at (800) 853-1964.

What is the UME Contingency Fund?

The Marine Mammal Unusual Mortality Event Fund is used by the Secretary of Commerce, in consultation with the Secretary of the Interior:

• “To make advance, partial, or progress payments under contracts or other funding mechanisms for property, supplies, salaries, services, and travel costs incurred in acting in accordance with the contingency plan issued under section 1421c(b) of this title or under the direction of an Onsite Coordinator for an unusual mortality event designated under section 1421c(a)(2)(B)(iii) of this title;
• For reimbursing any stranding network participant for costs incurred in the collection, preparation, analysis, and transportation of marine mammal tissues and samples collected with respect to an unusual mortality event for the Tissue Bank; and
• For care and maintenance of marine mammals seized under section 1374(c)(2)(D) of this title.”

The National Contingency Plan for Response to Unusual Marine Mammal Mortality Events outlines the types of expenses that are reimbursable under the fund and the process for requesting reimbursement.

Learn more about the UME Contingency Fund

How can deposits be made into the UME Contingency Fund?

The following can be deposited into the fund:

• Amounts appropriated to the fund
• Other amounts appropriated to the Secretary for use with respect to UMEs
• Amounts received by the United States in the form of gifts, devises, and bequests under subsection (d) (see 16 USC 1421d(d)).

You can use Pay.gov to donate to the UME Contingency Fund for this or other UMEs and help cover costs incurred by the Marine Mammal Stranding Network.