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Ashizuri-Uwakai NP, Kochi
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Kashiwajima’s winter heda-zushi turns yellowtail trimmings into a delicacy: a little skin stays on, and the salted fish is vinegar-cured with wasabi. Locals trace this island recipe to the Meiji era.
Moored boats can look airborne here: visibility can exceed 30 m, and pale granite-derived sand lets a boat’s shadow show on the shallow seabed. It’s a real optical trick, not floating magic.
Otsuki families traditionally welcomed the New Year with koshimeshi rather than soba: rice mixed with tiny fish, pickled radish and winter rock seaweed called menori. Gatherers once waded chest-deep to collect it.
By 2013, 1,150 fish species had been recorded in the waters around Kashiwajima—the highest count for a limited area in Japan. Subtropical and temperate fishes overlap where the currents meet.
Kashiwajima’s shore grows hamabofu, an aromatic wild coastal plant. Locals traditionally mix it into shira-ae, a tofu dressing—turning a plant from the beach into a distinctive side dish.
When squid catches fell, fishers and divers built underwater spawning beds from branches, with children joining in. Branch spacing mattered: one well-used bed attracted as many as 10,000 egg clusters.
Island students once gathered tengusa seaweed to help pay for school trips: skilled swimmers picked it underwater while others collected strands washed ashore to dry. The fishers’ cooperative let them start just before the season opened.
Decades ago, a set net about 100 m offshore reportedly caught as many as 2,400 yellowfin tuna in a single day. That fishery has ended, but tuna and sea bream are now farmed in the bay.
Near Kashiwajima, Komame is famed for a 300-m-wide cluster of Pavona decussata corals described as Japan’s largest. Nearby Kannonzaki has a record colony of mushroom-shaped Leptoseris papyracea.
A new goby species was identified from an artificial reef retrieved off Kashiwajima. The reef had spent 2.5 years at about 100 m depth, and the single specimen used to describe the fish measured just 28.8 mm.
A survey of the wider 100–300 m seafloor around Kashiwajima, Okinoshima and Cape Ashizuri yielded 1,792 mollusc species, according to Japan’s Environment Ministry—a remarkable deep-water inventory, not a beach count.
A 1589 land survey listed 28 house sites on Kashiwajima, including 17 occupied homes and 2 boat-storehouse sites. It also recorded resident sailors and ship captains—evidence of a long-standing seafaring community.
An Edo-period stone barrier, about 200 m long, was built across Kashiwajima’s swift channel. By creating a shallow that turned migrating tuna toward the harbor, it helped turn a tricky current into a fishing ground.
Until the 1990s, tengusa seaweed blanketed rocks around Kashiwajima. Locals raked or free-dived for it, dried it on the quay and auctioned large bales near the shrine; buyers came from as far away as Nagano to make agar.
