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Hundreds of harbor seals live in Iliamna Lake, the largest body of freshwater in Alaska and one of the most productive systems for sockeye salmon in the Bristol Bay region.
These lake seals are a robust yet highly unusual and cryptic posse. Although how the seals first colonized the lake remains a mystery, it is thought that sometime in the distant past, a handful of harbor seals likely migrated from the ocean more than 50 miles (80 kilometers) upriver to the lake, where they eventually grew to a consistent group of about 400. These animals are important for Alaska Native subsistence hunting, and hold a top spot in the lake's diverse food web.
Scientists - Colonizing - Seals - Lake - Offspring
Scientists now know these "colonizing" seals must have found the lake suitable enough to stay and raise their offspring. Generations later, the lake-bound seals appear to be a genetically distinct population from their ocean-dwelling cousins—even though they are still managed as part of the larger Eastern Pacific harbor seal population.
But if the lake seals are distinct and show signs of local adaptation to their unique ecological setting, this would mean that their conservation—especially in the face of the rapidly changing climate of western Alaska and proposed industrial developments—should differ from that of nearby marine populations.
Chemical - Records - Canine - Teeth - Show
Lifelong chemical records stored in their sequentially growing canine teeth show that the Iliamna Lake seals remain in freshwater their entire lives, relying on food sources produced in the lake to survive. In contrast, their relatives in the ocean are opportunistic feeders, moving around to the mouths of different rivers to find the most abundant food sources, which includes a diverse array of marine food items in addition to the adult salmon returning to Bristol Bay's nine major watersheds. These findings are described in a paper published online in March in Conservation Biology.
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