The 2019-2023 Gray Whale UME

    San Diego has many ways to interact with marine mammals and ocean life. One of these ways is by whale watching with plenty of places to go in San Diego. However, since 2019 Gary Whales have seen their population dip significantly. 

 

    As lengthy research is done there, maybe a larger trend. According to a 2022 assessment of the Abundance and migratory phenology of eastern North Pacific gray whales 2021/2022 conducted by the Southwest Fisheries Science Center, the population had decreased by 38% since 2016. In 2016 the number of recorded migrating whales along the West Coast was 27,000 and in 2022 it was 16,650.

 

   Sometimes when these populations decrease it can be a sign of a Unusual Mortality Event. Sara Mesnick Ecologist and Science Liaison for the National Oceanic and Atmospheric Administration, talks about what a UME is, as defined by the Marine Mammal Protection Act, she states it is “a stranding event that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response.” There are also seven criteria that put a mortality event into the unusual category. 

The seven criteria, according to the National Oceanic and Atmospheric Administration’s website, are listed below.

 

“The Working Group on Marine Mammal Unusual Mortality Events developed a set of criteria for determining an unusual mortality event:

1. A marked increase in the magnitude or a marked change in the nature of morbidity, mortality, or strandings when compared with prior records.

2. A temporal change in morbidity, mortality, or strandings is occurring.

3. A spatial change in morbidity, mortality, or strandings is occurring.

4. The species, age, or sex composition of the affected animals is different than that of animals that are normally affected.

5. Affected animals exhibit similar or unusual pathologic findings, behavior patterns, clinical signs, or general physical condition (e.g., blubber thickness).

6. Potentially significant morbidity, mortality, or stranding is observed in species, stocks, or populations that are particularly vulnerable (e.g., listed as depleted, threatened, or endangered or declining). For example, stranding of three or four right whales may be cause for great concern whereas stranding of a similar number of fin whales may not.

7. Morbidity is observed concurrent with or as part of an unexplained continual decline of a marine mammal population, stock, or species.

   Any of these criteria may indicate an unusual mortality event.

   For more information, see the Federal Register notice (71 FR 75234), published on December 14, 2006, that announced these criteria.” 

 

    In 2019 several gray whales began stranding themselves along the west coast of North America, NOAA scientists looked into the event and determined it was a UME. Since 2019, these scientists have documented the number of strandings and accessed the event’s data in search of a cause. There are several factors that can cause a UME including natural infectious diseases, biotoxins, ecological factors, human interactions and a majority that are undetermined. 

 

   Scientists with the NOAA are working as they collect data to determine the cause. “They’re trying to figure out how these things that are not isolated may be acting together to get the patterns that we are seeing,” says Mesnick.

The undetermined UMEs account for almost half of the total UMEs since 1991. In the pie chart provided by the NOAA below, you can see the most common causes of UMEs among all marine mammals.

 

   

 

 

 

 

 

 

 

 

 

 

    The gray whale UMEs effect has been seen across San Diego by a local whale-watching captain, Cici Sayer, Owner of Offshore Blue Adventures. “There was a significant die-off of some whales a few years ago, and that was pretty well documented,” said Sayer. This year, however, as the mortality rate has significantly decreased the populations have bounced back. “As for this year, I would say that we had a healthy number of whales, I wouldn’t say is was more or less,” said Sayer.

Sayer also has seen a trend with the whale populations specifically here in San Diego. She claims Gray Whales are specifically avoiding this area.

“In San Diego, we do not see the northbound whales like we used to because they are apparently avoiding the area. Up in Newport Beach, they’re still seeing migrating Gray Whales going through the north; we have not seen any in weeks, and they are seeing them all along the coast. There is a lot of speculation as to why, and a lot of people seem to feel it might be the Navy and their high sonar exercises that they do off the California coast; might also be that there are so many boats in San Diego that go out and are not observing the best practices for whale watching. I’m talking about private boats. So these whales have to navigate an onslaught of boats. The speculation amongst a number of whale-watching companies is that the whales are starting to avoid the area,” said Sayer. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A packed West Basin Harbour is pictured above.

 

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Boats scattered across the Sunset Cliffs horizon.

This lack of whales in San Diego specifically can be seen on the map provided by the NOAA that records whale strandings and their location. 

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   In the map, there are more recordings of whale strandings south and north of San Diego County specifically. Even more, recordings are above and below Southern County in general.

While scientists are actively studying these UMEs many never have a determined cause. This is something that many researchers struggle with. Sunny Chung a 3rd year at Point Loma Nazarene, who participated in summer research, describes what research can be like.

“I would say, in general, a lot of experiments, you can't really expect and result, and a lot of times, many procedures, they don’t work. You have to look for new procedures because chemical reactions are not expected to happen. They happen when they when nature wants them to happen.” said Chung.

As these scientists have documented the number of strandings in North America each year there has been a gradual decrease. However, the number over the past two years and specifically this year has decreased drastically, going from 47 strandings last year to 9 this year (see NOAA data chart below).

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   Though scientists have been studying this UME since 2019 the cause is still undetermined and requires more research. They did, however, find that many of the whales that were stranding themselves were doing so due to exhaustion, although the specific cause of the exhaustion was unclear. Dr. Amiée Lang is a scientist studying the Gray Whale UME and researched the data and information in the report of Abundance and migratory phenology of eastern North Pacific gray whales 2021/2022. She was able to expound on the specific predetermined effects of the exhaustion, what food sources look like for whales in general, as well as specifically for gray whales. “Several of the whales have been emaciated, suggesting that they may have experienced a food shortage. However, not all whales have been thin, and in some cases the cause of death has been due to other factors. So basically we can’t point to one exact cause of the UME (it is considered ‘undetermined’, although we think it is being driven in part by changes in prey availability on their Arctic feeding ground. Although gray whales do eat krill occasionally, they aren’t krill specialists like some of the other baleen whales and they in fact eat a wide range of prey – amphipods, crustaceans, mysids, and polychaetes are all part of their diet. My guess is that they don’t eat enough krill for that one prey item to have a large impact on their health, but certain changes in prey availability more generally seems to be a factor in the most recent UME”, said Lang.

In  GRAY WHALE (Eschrichtius robustus): Eastern North Pacific Stock (p. 162) a 2019 assessment, there was a hypothesis of the cause of the initial census of whale stranding in the West Coast. It said, “The Evidence indicates that the Arctic climate is changing significantly, resulting in a reduction in sea ice cover that are likely to affect gray whale populations (Johannessen et al. 2004, Comiso et al. 2008). For example, the summer range of gray whales has greatly expanded in the past decade (Rugh et al. 2001). Bluhm and Gradinger (2008) examined the availability of pelagic and benthic prey in the Arctic and concluded that pelagic prey is likely to increase while benthic prey is likely to decrease in response to climate change. They noted that marine mammal species that exhibit trophic plasticity (such as gray whales which feed on both benthic and pelagic prey) will adapt better than trophic specialists.” 

 

   Scientists were working in the field from April 24- April 28, 2023, to try and determine the cause of these whale strandings. Dr. Lang comments on this hypothesis and if it has proven true “There are indications that the availability of prey in the Arctic has changed in recent years. However, scientists are still working on better understanding this impact. Some work suggests that while prey in some areas has declined, the prey base in other areas is stable or even increasing. As well, while certain prey species have declined, others have increased. Thus the changes are complex and we are still working on understanding the impacts to gray whales.”

 

   She also, however, addressed the prediction of the effect of the melting ice near the Chukchi Sea up near Alaska that has been predicted to be having an impact on food sources for whales including gray whales recorded by the NOAA. The impact could also be seen in 2016 in the Chukchi Sea as Whales migrated north.  

Dr. Lang said, “The gray whales that are counted during the aerial surveys of the NE Chuckchi Sea are part of the same population as those that migrate along the west coast of North America, so factors affecting the whales in the Chukchi are also affecting those migrating past the US west coast. There are currently no other UMEs declared for cetaceans in the North Pacific, although a UME for ice seals (bearded, ringed and spotted seals) was also declared in 2019 (and is in the process of being closed as I understand). The cause of that UME was also considered undetermined, so we can’t say if there is a relationship between the two events.”

 

   Scientists are working to determine the exact cause of this UME but have learned a lot about the Gray whale population and the effects of the environment on their species.

For the most up-to-date information on the locations of whale strandings can be found in an interactive map on the NOAA website.

 

 

THE MOST IMPORTANT ACTION SOMEONE CAN TAKE IS TO IMMEDIATELY REPORT A DEAD, INJURED, OR STRANDED MARINE MAMMAL. MAKE THE REPORT BY CALLING IN CALIFORNIA, OREGON, OR WASHINGTON THE WEST COAST MARINE MAMMAL STRANDING NETWORK: 1-866-767-6114, IN ALASKA THE ALASKA MARINE MAMMAL STRANDING NETWORK: 1-877-925-7773, AND IN CANADA, THE BRITISH COLUMBIA MARINE MAMMAL RESPONSE NETWORK 1-800-465-4336.

YOU CAN ALSO CONTACT THE U.S. COAST GUARD ON VHF CHANNEL 16. DO NOT APPROACH OR TOUCH INJURED OR DEAD MARINE MAMMALS.

ALL MARINE MAMMALS ARE FEDERALLY PROTECTED BY THE MARINE MAMMAL PROTECTION ACT. ONLY LOCAL AND STATE OFFICIALS AND PEOPLE AUTHORIZED BY NOAA FISHERIES MAY LEGALLY HANDLE LIVE AND DEAD MARINE MAMMALS.