The Nature of the Shimanto River
The pristine water of the Shimanto River supports a diverse ecosystem, from algae and plankton to fish and birds. As the river meanders for 196 kilometers from its source on Mt. Irazu (1336 m) to the Pacific Ocean, it passes through the densely forested mountains and fertile floodplains of western Kochi Prefecture. The river has few dams and embankments, and the area it flows through is largely undeveloped. Small villages along the river are connected by simple, submergible bridges designed to weather annual floods. These communities have learned to live in harmony with the river that supports their way of life.
Supporting aquatic life
Ayu (sweetfish), red-spotted masu trout, eel, goby, tenaga-ebi (long-armed river shrimp), and Japanese mitten crab thrive in the middle and lower reaches of the river. Sustainable fishing practices including limited fishing seasons are used to prevent overfishing in this area.
The river reaches the Pacific Ocean near the town of Nakamura. Here, upwards of 200 species of fish thrive in the brackish waters of the Shimanto River estuary, including the rare akame (Japanese lates), which is similar to a barramundi. Aosa nori (green laver) seaweed grows in the briny water and is harvested by hand and dried on frames next to the river in winter. It is prized for its soft, chewy texture and high mineral content and sheets of it are often deep-fried as tempura.
Wildlife sanctuaries and parks
Several conservation areas protect the insects and birds that live around the Shimanto River. More than 60 species of dragonfly inhabit the Dragonfly Sanctuary Park in Nakamura, attracted by environmental factors such as water quality, humidity, and temperature. They only lay their eggs in clean-water environments that have healthy populations of small aquatic insects for the nymphs to feed on.
The Shimanto River Wild Bird Nature Park near the mouth of the river is a habitat for grassland birds, including great reed warblers and meadow bunting. Visitors can see the birds up close from observation huts in the park. Deep in the mountainous area near the middle reaches of the river, the Yairocho Trust NGO near the village of Shimodo protects migratory colonies of colorful fairy pitta that come from Southeast Asia in May to breed. The Shimanto area is one of few places in Japan where these birds can still be seen.
Forests and flowers
The Shimanto River’s mild, humid environment is ideal for a variety of flora. Plant habitats along the river vary according to the terrain. In the middle and upper reaches of the river, rhododendrons, Japanese silver grass, oak, beech, and chestnut trees flourish. These varieties are also planted along the riverbanks to prevent erosion.
On the lower reaches of the river, the Nyuta Willow Forest covers roughly two kilometers of land near the town of Nakamura. From late February to March, the forest floor is covered in vivid yellow canola flowers. In late spring, 23 varieties of wisteria bloom through Kosanji Citizen’s Park and the grounds of Kosanji Temple. Wisteria blossoms are a prominent decorative motif in Nakamura. They featured on the crest of the Ichijo family, which contributed to the development of the town in the fifteenth century. In early May, the plant is celebrated at the spring Wisteria Festival. From late May, hydrangeas serve as a colorful backdrop for the Yasunami Water Wheels near the town center.
