Unusual Mortality Event (UME) Determined for NEP Gray Whales

Unusual Mortality Event Announced for Gray Whales

You have probably heard in recent weeks Media reports about the unusual increase in the strandings of dead and emaciated gray whales along the Western Pacific coast of North America. On Friday 31 May 2019 the U.S. National Oceanic and Atmospheric Administration’s Fisheries Service (NOAA Fisheries) announced that the recent elevated rate of gray whale strandings along the West Coast of the United States constitutes and Unusual Mortality Event (UME). View the NOAA announcement:


LSIESP researchers monitoring the gray whales in Laguna San Ignacio and Bahía Magdalena, Baja California Sur, Mexico detected indications an impending UME as early as last year (2018) and again in 2019. LSIESP long-term monitoring and research program allows the detection of departures from the “normal” abundance and mortality trends for gray whales in their winter Baja breeding lagoons. Specifically, they documented declining calf counts, increasing percentages of “skinny” and “emaciated” whales, and the late arrival of the whales to the Baja lagoons.  Read more about:

Declining gray whale calf production and late arrival at the Baja lagoons

Gray whale body condition

Of particular concern is our lack of understanding of the underlying cause of such mortalities. Perhaps the “carrying capacity” of the gray whales’ feeding areas has been reduced during the past decade.  Oceanographers are describing conditions of warmer-than-normal sea temperatures in the North Pacific/Gulf of Alaska and along the west coast of North America that have persisted from 2015-present. This temperature anomaly is disrupting the normal seasonal cycle of primary production during the spring and summer months in the high latitudes where the gray whales, and other marine life feed.  Gray whales depend on the summer abundance of prey to obtain sufficient energy to survive their winter/spring migrations to and from their winter breeding and calving areas, and the production and growth of their calves. Skinny gray whales and low calf production, and now increased mortalities during migration, suggest that finding sufficient food over the summer is becoming a problem for the gray whales.

Read more about the changes in the North Pacific Ocean that could contribute to food limitation for gray whales and other marine life:




So what are we doing? LSIESP researchers continue to monitor the whales’ abundance and calf births during the winter months in the Baja lagoons, and have implemented new research methods to document and evaluate the body and breeding condition of gray whales. UAV-Drones with HD-video allow our researchers to obtaining photogrammetric images to document the health of whales, their length and girth, and overall body condition. From photos of the same individuals obtained over the three month winter they calculate the rate of weight loss for lactating females, and the growth rates of newborn calves. Over time these data will allow the evaluation of trends in gray whale health and growth during the winter months following their summer feeding in the North Pacific and Arctic. Read about LSIESP’s gray whale condition research in our 2019 Annual Research report:


We need your help to ensure gray whale research and monitoring in the Baja lagoons continues

Now more than ever there is a need to continue monitoring gray whales during the winter in the Baja lagoons. Determining the impact of the UME and (hopefully) tracking the recovery of the whales will require gathering as much information as possible during the coming winter to document the conditions of the whales following their summer feeding, their abundance, and the number of calf births. This information will help scientists and the public understand what is happening to the gray whales, and hopefully identify environmental and other factors that may contribute to these increases in mortality.

Please become a “sustaining” supporter of LSIESP

With your credit card you may safely and securely arrange a monthly donation to ensure that LSIESP gray whale researchers are able to provide much needed information on the whale’s status.  Just $5.00 each month ($60.00 each year) can help pay for the consumable necessities of the field work each winter, and provide support for LSIESP university researchers. Your recurring contributions will continue each month until you tell us to stop.

Please visit our website to make your tax deductible donation through our non-profit fiscal sponsor “The Ocean Foundation.” We need your support to maintain a comprehensive research program:


Thank you for your support!

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