As the Bering Sea warms and transforms, marine animals of all types are moving north — including some of the world’s most critically endangered whales. And that may spell some new trouble for the tiny population.
Since 2016, one or more North Pacific right whales have been heard and seen in the northern Bering Sea and Bering Strait region, well north of the southern Bering Sea and Gulf of Alaska waters considered to the main habitat of the critically endangered Eastern Pacific population.
The move into the Bering Strait area raises some worries.
The Eastern North Pacific population that swims off Alaska is the most endangered of all the world’s large whale populations, numbering only about 30 animals, according to the National Oceanic and Atmospheric Administration.
And the narrow Bering Strait is becoming increasingly crowded with ship traffic, a trend expected to increase as Arctic ice continues to retreat.
“Obviously, with the right whale presence in any kind of chokepoint or any kind of narrow strait where vessel traffic occurs, there’s increased risk,” said Jessica Crance, a marine biologist with NOAA’s Alaska Fisheries Science Center who has been studying the elusive whales.
The movement north is “really bad news for the right whales,” Catherine Berchok, also of NOAA’s Alaska Fisheries Science Center, told the audience at last month’s Alaska Marine Science Symposium in Anchorage.
Signs of right whales in the far northern part of the Bering started coming in through an acoustic monitoring network. The distinctive right whale songs were recorded from August to November of 2016, and also in 2017 and 2018, said Dana Wright, a Duke University marine scientist who has been tracking the rare whales by sound. Data from 2019 is still being analyzed, Wright said.
On top of the sound evidence is visual evidence.
Scientists doing a survey for the International Whaling Commission in 2018 sighted — and photographed — one right whale swimming off St. Lawrence Island in the Bering Strait region, Crance said. The same whale appeared weeks later in a Russian fjord, where it was photographed again, she said. And last summer, a local resident spotted a right whale in the same St. Lawrence Island area, though no photographs were taken, so it is unclear whether that was the same or a different individual, Crance said.
With a population this tiny and mysterious, it is hard to know exactly what is behind the northward movement, Crance said. It could be that the whales are returning to habitat they used in the long-ago past, she said. It could be a result of a periodic Bering Sea regime shift between cold and warm periods, she said. Or it could be the product of climate change, she said. “It could be any of those three. It could be a combination of those three,” she said.
In both the Pacific and Atlantic, right whales were hunted nearly to extinction by commercial whalers starting in the early 19th century. To commercial hunters, these were the “right” whales to kill because they swam slowly and had such high fat content that they floated when dead.
Now small numbers of right whales survive in northern waters of the Pacific and Atlantic. There is a Western North Pacific population numbering a few hundred that swims off Russia and Japan in addition to the very tiny Eastern North Pacific population of Alaska, which has been designated a distinct population segment. The North Atlantic right whale population is also highly endangered, numbering only about 400 individuals, according to NOAA.
Ship strikes are considered one of the top risks to right whales in both the North Atlantic and North Pacific.
From all signs, the tiny Eastern North Pacific right whale population has been concentrated since the 1960s in the southeastern Bering Sea and part of the Gulf of Alaska. Federal regulators in 2008 designated those areas as critical habitat for the tiny population.
No special regulations have been put in place yet for that critical habitat, Crance said. It is an important area for commercial fishing and ship travel, but the right whale population there is so small and individuals are so rarely seen that “it’s extremely difficult for us to quantify the risk,” she said.
If right whales are being drawn farther north, they are part of a larger whale trend off Alaska.
Chukchi Sea beluga whales have delayed their fall migration south, research shows. Chukchi belugas were migrating south two to four weeks later in the 2004-2012 period than in the decade prior, according to a study led by the Donna Hauser, then with the University of Washington but now with the University of Alaska Fairbanks.
Hauser and her colleagues also found that while they were in the Chukchi in the summer, belugas are diving deeper to find their food.
Bowhead whales are also lingering longer in the Chukchi Sea during their fall migrations south to the Bering, scientists have found. Prior to 2012, bowheads generally passed quickly through the Chukchi on their journey south, but that has changed since that year, which posted record-low sea-ice extent, according to a study by the Alaska Department of Fish and Game. In recent warm conditions, some bowhead whales overwintered in the Chukchi Sea, skipping the usual migration south into the Bering Sea, according to observations reported in a study published in the journal Nature Climate Change.
Meanwhile, killer whales are moving north into the region, as evidenced by recorded sounds and by increasing bite wounds on bowheads.
A study of harvested bowhead whales harvested between 1990 and 2012 revealed a marked increase in scarring from killer whale bites since 2002, a strong sign that those predators have moved in from the south.
By 2015, there were about three times as many killer whale calls in the southern Chukchi Sea during the fall season as there were in 2009, according to a study based on sound recordings and published a year ago in the journal Marine Mammal Science. The study, by Katherine Stafford of the University of Washington, noted that by 2015, the Chukchi’s open-water season had expanded by six weeks over the prior 30 years.
To better understand what marine mammals are doing in the rapidly transforming Bering Sea environment, one scientific team has collected data from a first-ever year-round acoustic monitoring program in the Bering Strait region.
The group, led by scientists at the Wildlife Conservation Society, used sound-collecting devices mounted to the seafloor off Gambell and Savoonga, villages on St. Lawrence Island, and directly in the Bering Strait. Between 2012 and 2016, the scientists collected over 33,000 individual calls from bowhead whales, beluga whales, walruses, bearded seals and ribbon seals.
The results, which showed distinct seasonal patterns, are detailed in a study published in the journal Marine Mammal Science. The study’s authors said it provides baseline information that will be important to have as the region continues to warm — and becomes subject to more disturbances from vessel traffic, the authors said.
“There is no doubt that the Arctic is currently undergoing rapid and significant changes that are alarming,” said Dr. Howard Rosenbaum, director of the Wildlife Conservation Society’s ocean grants program, said in a statement. “Our work on Arctic marine mammal populations in this region is essential to assess any forthcoming resulting shifts or changes resulting from warming Arctic conditions, and ultimately working partners and authorities to find solutions to protect these iconic species and their habitats.”