SPARS Helps Marine Biologists and Alaskan Natives Count Seals

SPARS Helps Marine Biologists and Native Alaskan Hunters Sample Alaska Harbor Seals

For Alaska's Ecosystem and Its Native Culture, Harbor Seals are Critical
One hundred and two people live in Tatitlek, Alaska, a traditional Alutiiq village in a forested coastal glen - the impassible Chugash Mountains, like snowy ramparts, at their backs and the vast Prince William Sound spreading out before them. Intimately linked to the mountain and sea that surround them, Tatitlek is much like the hundreds of native Alaskan coastal communities for whom a subsistence lifestyle is tradition, and for whom harbor seals (Phoca vitulina) play a central role in a community’s diet and, because of that, its culture.  

In 2008, of the 1,462 harbor seals harvested in the state of Alaska, Tatitlek harvested 141 of them. With one harbor seal supplying about 56 pounds of useable meat, fur, and oil, every person in Tatitlek, had 77.4 pounds - about a quarter pound of seal a day - 39% of their meat that year.

Not only are harbor seals important to native Alaskan people, they are both a key marine predator and an important prey animal, and they live in a nearly unbroken sweep of coast from Dixon Entrance south of Juneau, west more than a thousand miles curving down
the Aleutian Archipelago, then north to Kuskokwim Bay in the Bering Sea.

But, since the 1970s, throughout that wide distribution, the Alaskan harbor
seal population - which is divided into three "stocks" for wildlife management
purposes - has declined precipitously - west of the Gulf of Alaska,
populations have dropped by 50 to 90%, but the decline is a strange, erratic one
- populations are relatively stable in the southeast. The cause or causes are unknown – ideas include predation and/or competition from stellar sea lions or sharks, resource competition from recently returned hump-backed whales, pollution, and temperature increase.

SPARS Review: Genetic Research Finds Alaska Harbor Seal Stocks Too Few For
Healthy Management

In 2005, in response to a request by the National Marine Fisheries
Service (NMFS)/Alaska Native Harbor Seal Commission, the Southwest
Fisheries Science Center (SWFSC) submitted the report "The analysis of
population genetic structure in Alaskan harbor seals (<i>Phoca
vitulina</i>) as a framework for the identification of management
stocks" by O'Corry-Crowe et al. SPARS directed its peer review, assembling a panel of five reviewers - two anonymous,  all experts in conservation ecology, biostatistics, and marine mammal biology.

The research they reviewed sampled 881 harbor seals in 180 sites, evaluating population subdivisions and seal dispersal patterns using mitochondrial DNA. The data indicated that the three stock units used by the state to manage marine mammal populations inappropriately lump together up to 12 smaller, genetically distinct populations. They concluded that continuing to manage the population using stocks too large, risks the extirpation of the smaller, genetically distinct sub-groups, reducing genetic diversity -  that variation within species that allows populations to adapt to environmental changes, resist certain diseases, and avoid inbreeding.

<blockquote>...managing the population using stocks too large, risks the
extirpation of the smaller, genetically distinct sub-groups. </blockquote>

In addition to identifying genetically distinct populations, the O'Corry-Crowe report also suggested that the spatially erratic nature of the drops in harbor seal population were actually reflecting the unrecognized sub-population diversity as those sub-populations responded (well, or less well) to predation, prey abundance, resource competition, and pollution. The report stated that the population declines were occurring "on similar spatial scales to the genetic findings presented," and that declines did not correspond "to currently recognized stock structure".

In Rocky Inlets and Drifting Pack-Ice: It’s Hard to Count Harbor Seals
After the two-day review in Juneau, the three on-site SPARS peer reviewers agreed with the investigators' conclusions generally, but recognized that sample coverage in data collection had been limited. It's tremendously difficult and expensive to sample or count harbor seals. They live most of their lives in the water, hauling out in rocky inlets and
pack-ice only to pup and molt, they are similar in appearance to other seals making them hard to discern from a distance, and they are scattered across enormous fields of floating ice that shift with ocean and wind currents.

Because it’s so hard to sample and monitor harbor seals, it was recognized that identification of meaningful management stocks should incorporate traditional Alaskan ecological knowledge. Native knowledge is frequently employed to interpret trends in harbor seal distribution, abundance, and foraging ecology relevant to stock structure. In fact, researchers stated that "active collaboration with Alaska native subsistence hunters and directed sampling is necessary" to cover difficult-to-sample areas.

<b>Alaskan Traditional Ecological Knowledge Used to Monitor and Count
Harbor Seals</b>

Scientists monitoring Alaska wildlife routinely collaborate with native hunters. Since 1997, indigenous hunters, the only group legally allowed to hunt harbor seals, have provided the Alaska Native Harbor Seal Commission with biosamples of their kills. Whiskers identify changes in diet. Blubber, kidney, and liver samples are tested for heavy metal contaminants, protecting both seal populations and public health. Hunters collect skin samples to monitor, as in the O’Corry-Crowe study, stock identity to understand how closely related harbor seals are in different parts of the state.

Not only do native hunters work with scientists to collect biological samples, but because a subsistence lifestyle requires exceptional skill and traditional knowledge of resources and the environment, native hunters are a valuable resource for qualitative information, guiding scientific enquiry.

Beth Mathews, Assistant Professor of Biology at the University of Alaska Southeast, who attended the O’Corry-Crowe review, gives an example in which "a hunter in Yakutat had observed harbor seal pups in the stomachs of sleeper sharks. That raised new ideas about population pressures on harbor seals, and inspired research into whether those pups were being eaten live or not, looking at sleeper sharks as either a predator or a scavenger.”

That Yakutat hunter had spent a lot of time out in the field, said Mathews, and had the expertise to notice it was something unusual. “Traditional knowledge was extremely valuable in bringing this important ecological interaction to the attention of scientists. The decline in harbor seals - 70% Glacier Bay since 1990 - cautiously suggested that sleeper sharks were responsible.”

Anne Hoover-Miller, scientist at the Alaska Sealife Center who also attended the review, agrees that, because "…native seal hunters are out in the world out there, when they're catching seals," they can provide valuable qualitative information to researchers. At community meetings, she said, "…the hunters were really concerned about the loss of animals, then we'd hear there were improvements in the north. Those are my first clues,” she says, “that a region is showing improvement or that they’re concerned about this."

"NMFS has a hard time surveying because of weather, but the local people can take advantage of the weather more easily and fill in the gaps." Sentinel programs, notably the Aleutian archipelago's Aleut Mammal Commission, and harvest monitoring program through the Alaska Native Harbor Seal Commission are extremely useful. “If native hunters think something is amiss, it probably is."

<blockquote>"Yakutat hunters have been concerned that the number of seals were going down, hunter insight can trigger hypothesis generation. If native hunters think something is amiss, it probably is.""</blockquote>