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Chichibu-Tama-Kai NP, Tokyo
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The stream-breeding frog Nagare-tagogaeru (Rana sakuraii) was first found in Nippara in 1978; Nippara River is its type locality, and scientists formally described it in 1990. Unlike most frogs, it breeds in flowing water.
A Nippara tributary yielded a wild iwana–yamame hybrid. Its mottled back inspired the nickname kawa-saba (“river mackerel”); locals reportedly call such fish unnei, and DNA showed this fish’s mother was iwana.
Nippara drains about 90.8 km²—7.3% of the Tama basin—yet its water supplies most of the Tama’s channel flow between Ogouchi Dam and Mitake No. 1 Power Station. Much upstream water is piped past this reach for hydropower.
Yamame occur in Nippara, and Tokyo developed a larger food strain, Okutama yamame, in 1998. Its size lets local cooks serve it as sashimi, sushi, meunière or fried fish—not just as a small grilled stream fish.
Nippara Limestone Cave lies on Ogawa Valley, a Nippara tributary. Local accounts describe it as a Shugendo pilgrimage place devoted to Dainichi Buddha; a tiny stream inside was nicknamed Sanzu no Kawa, the “River of the Three Crossings.”
Timber once floated down Nippara toward Edo, while residents made white chopsticks from mizuki wood. The craft gave the village its nickname Hashikaki—“chopstick-splitting village”—and was once a livelihood across the community.
Tokyo began managing forest at Nippara’s headwaters in 1901, taking over about 320 hectares of imperial woodland and placing another 5,100 hectares in the basin under protective forest status to safeguard the water source.
In November 2023, a Tokyo survey netted 94 fish of 6 species in Nippara. Across monitoring from 2008 to 2023, researchers found 7 species and reported no sharp decline in native fish or surge in newly introduced species.
Tokyo’s Okutama fish center raises Nikko iwana derived from the Nippara River system—so this stream is not only home to the char, but also a source of fish used in local hatchery production.
Exposed limestone in the Nippara district launched a surprising transport story: the company developing it was formed in 1937 to move stone, and its 9.76-kilometer railway was taken over by the state and opened as the Ome Line in 1944.
