The harbor seals of Alaska’s Iliamna Lake, which make up one of only five freshwater seal populations in the world, have long been a subject of fascination for their separateness from the seals that swim in the nearby ocean waters.

Now scientific research has confirmed something that has long been suspected: The Iliamna Lake seals, believed to number about 400, are genetically different from the harbor seals swimming in the saltwater of Bristol Bay and the wider Pacific Ocean.

The findings are in a study published in the journal Biology Letters. The study is a collaboration of scientists from Florida Atlantic University, the University of Alaska Fairbanks, the University of Washington, the National Oceanic and Atmospheric Administration and Seattle-based North Pacific Wildlife Consulting.

Co-author Greg O’Corry-Crowe, the Florida Atlantic University research professor who did the laboratory analysis, said the genetic differences between the Iliamna Lake seals and the seals in Bristol Bay, which is connected to the lake by the Kvichak River, and the ocean beyond were striking. “They kind of jumped off the page, as it were,” he said.

What he does not yet know is how long the seals of Iliamna Lake, which is Alaska’s biggest lake, have been separated from the ocean seals. The period could extend for thousands of years, possibly back to the end of the last Ice Age, he said, but it will take further work to pin that down.

“All we can say definitively, through Indigenous knowledge and early Russian account, is they’ve certainly been there for a number of centuries,” he said.

The genetic results are from tissue samples taken from seal bodies and from seal scat collected over two summers from the lake’s shorelines.

Tissue samples were supplied by local Native subsistence hunters; the scat samples were supplied by study co-author Donna Hauser, a marine mammal biologist at UAF.

Hauser has been intrigued by both the lake and its seals for years. Her study of them dates back to her time as an undergraduate at the University of Washington, when she traveled to the lake to work on a research project about their diet.

In later years – 2015 and 2017 – she jumped at the chance to make more trips there when her husband, UAF fisheries biologist Peter Westley, was headed to Iliamna Lake for salmon fieldwork. They brought along their young son, Finn, and enlisted him in her sample collection. “It was sort of a fun game,” Hauser said. “I was, like, ‘OK, can you go find the seal poop?’”

The new findings add to other evidence about Iliamna Lake seals’ uniqueness, including a previous study of teeth that used isotope analysis to show that the animals were staying in the freshwater environment year-round.

A key difference from their saltwater seals is the Iliamna Lake seals’ ability to live with and under the ice when the lake freezes over, an unusual trait for harbor seals. Scientists still want to know more details about how they do that, and more: what they are eating, where they are in winter, how and when they haul out onto the ice or the shore and where they fit in the complex Iliamna Lake system

“Those are the really fascinating questions, from an ecology standpoint, for me. Like, how are these guys really able to make a living year-round?” Hauser said. “Of course, they’re feeding on salmon when salmon are super-abundant. But what are they doing when they’re not?”

Traditional Indigenous knowledge has long held that Iliamna Lake seals are different from their saltwater counterparts. Their fur is thicker and softer, for example, and their pupping season seems to be later, according to traditional knowledge. Written accounts of the seals’ presence in the lake go back 200 years, to the Russian era in Alaska.

In recent years, agency and university scientists put more focus on Indigenous knowledge. To that end, a monitoring program is being assembled by the Igiugig Village Council, the tribal government for the village at the west end of the lake.

The program will be holistic, said Mary Hostetter, the Igiugig Village Council’s tribal steward.

“When we think about our entire ecosystem, everything is so interconnected. You cannot take the seals away from the salmon or from the smelt or the whitefish without really taking a little pillar of their existence and how they live in relationship with the place,” Hostetter said during an online meeting held Oct. 29.

Management implications

Yet to be determined is whether new findings about the seal population’s separateness will lead to any significant management changes in the region.

The Endangered Species Act grants protections to what is known as “distinct population segments” that are under threat. An example of a protected distinct population segment is the Cook Inlet beluga whale population, with only about 300 animals and listed as endangered.

One environmental group that has sought Endangered Species Act listing for the seals has argued that the Iliamna Lake population qualifies for similar protection.

“Iliamna Lake seals exhibit special characteristics that demonstrate their unique biological and ecological role as a distinct population segment,” said a 2020 petition filed by the Center for Biological Diversity.

The petition, like an earlier petition filed by the group in 2012, cited the seals’ larger size, darker and finer fur than those of harbor seals in the region’s saltwater environments. It also cited the seals’ use of the lake ice cover and a different diet than that of saltwater seals, with freshwater fish likely making up a large share.

Threats to the seals, the petitions said, include the proposed Pebble mine project, which would use the lake area as a transportation corridor; climate change; and the small size of the population, which puts its very existence at risk from shocks like major disease outbreaks.

Elsewhere in the world, other freshwater seal populations are classified as endangered.

The Ungava seal population in northern Quebec, also known as the Lacs des Loups Marins seal, is the only other freshwater harbor seal. Classified as a subspecies of marine harbor seals, the Ungava population lives in the Lacs des Loups Marins lake and its associated rivers. The population estimate is as low as 50, according to the Canadian government, though numbers are uncertain. Both the Canadian government and the International Union for the Conservation of Nature have listed the population as endangered.

In Finland, the endangered Saimaa ringed seal population, which is confined to the lake for which the animals are named, is down to about 480 from an earlier estimate of 1,000, according to the World Wildlife Fund. The main threat identified by Finnish authorities has been climate change, which has erased a lot of the springtime snow that the seals use to build lairs to birth, nurse and protect their pups. Entanglement in fishing gear is another identified problem.

In recent years, volunteers have been piling up snow to create manmade drifts that the seals can use to dig lairs. There also are seal-safe fish traps being distributed by the Finnish Association for Nature Conservation.

But when it comes to the Iliamna Lake seals, NOAA rejected both listing petitions, concluding that the animals “are discrete from, but not ecologically significant to, the Pacific harbor seal subspecies.”

That remains the NOAA position, at least for now, despite the new genetic findings.

The genetics study does confirm that the lake seals are different, said Peter Boveng, a research analyst with NOAA’s Alaska Fisheries Science Center and a study coauthor. “I would call it discrete, or separate,” he said. But that is only half what is needed to qualify as a distinct population segment under the Endangered Species Act, he said.

The other half is significance to the larger population, Boveng said. “To be significant, you have to have evidence that the separate population would have to be important to the preservation of the broader population,” he said. So far, that evidence has not been produced, he said.

Hard evidence about Iliamna Lake seals and their place in the ecosystem is a bit scarce because it has been hard for scientists to do field work in such a remote place, he added.

Even if there is no dramatic change in management, the new study is contributing to a push for more research into the seals, including better communication with local communities, Boveng said.

O’Corry-Crowe, who has carefully avoided the term “distinct population,” also said there are many unanswered questions that deserve future study.

“We’ve shone a light on Iliamna Lake seals, a scientific light,” he said. But there is much more to learn, he said. “Because really, we’re incredibly ignorant about these seals.”

Note: This story has been updated to correct a quote from Peter Boveng, who described the seal population as discrete rather than distinct. 

Alaska Beacon

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