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Hidakasanmyaku Erimo Tokachi NP, Hokkaido
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A 2024 study linked seal-derived nitrogen to kelp growing beside Cape Erimo’s haul-out reefs, where kelp grew larger than on other Erimo coasts. Seal waste and prey remains may help fertilize this valuable local harvest.
About half of Japan’s harbor seals live around Cape Erimo, the country’s largest haul-out site. Dozens of reefs stretch about 1.5 km offshore, and seals use more than 10 rocky spots to rest and raise pups.
Spring pups weigh just under 10 kg at birth and can swim almost immediately. They nurse for about 6 weeks before becoming independent; parents and pups also touch noses in a behavior rangers call “Nose to Nose.”
The Japanese name Zenigata means “coin-patterned”: the seals’ pale rings and spots resemble old coins with holes. Look closely through a telescope and the markings that inspired their name become clear.
Unlike seasonal seal visitors, Zenigata seals stay in Japan year-round. At Cape Erimo, they use the same reef sites through the year for resting, raising pups, and molting.
In the 1970s, only about 50 seals were counted hauled out at Cape Erimo; by 2008, the count had reached 524. After hunting and reef-damaging works stopped, the species’ Japanese status was reassessed as Near Threatened in 2015.
Cape Erimo is the southernmost edge of harbor seals’ range in the western Pacific. Its breeding group is genetically somewhat distinct from other Japanese groups, making these seals a special local population.
When seals damage fish in Erimo’s set nets, local fishers call it “tokkari-gui.” Tokkari is an Ainu word for seal, so the phrase carries a local language into everyday talk about fishing and wildlife.
Erimo Seal Club began in 1990, bringing together local salmon-net fishers, tourism businesses, and former student seal researchers who had settled in town. The group grew from efforts to consider coexistence, not just protection or removal.
The ranger team’s seal-counting AI is called Seals123, but it can mistake a seal-colored rock for an animal—or miss a seal blending into the reef. People review and correct its detections before the count is final.
To keep seals out of the final compartment of salmon nets, fishers and officials test exclusion grids of different shapes and mesh sizes. Underwater cameras show how seals and fish approach, helping them refine the barriers.
Drone counts are timed for low tide, when more reefs emerge and seals haul out. But winds of 10 m/s or stronger blow at Cape Erimo on more than 260 days a year, so researchers must wait for a safe launch window.
