Lake Biwa

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Lake Biwa, Japan.
© WWF-Canon / Mima JUNKICHI

About the Area

Lake Biwa is one of the oldest lakes in the world, estimated to have originated some 4 million years ago. It covers 259 square miles, is 39 miles long, 14 miles across at its greatest width and less than one mile across at its narrowest.

Surrounded by mountains and fed by 460 streams, the lake has high species richness and endemism, with 38 snail (19 endemics), 16 bivalve (9 endemics), and 4 endemic fish species, in addition to 70 aquatic plants.

Lake Biwa hosts 491 species of plants and 595 species of animals. Recent studies of the lake bottom suggest that many more species remain to be discovered. About 50 species and subspecies are found nowhere else. These include such animals as the freshwater pearl mussel (Hyrlopsis schlegeri). Other species reach their southern limit in Lake Biwa, where they persist in the cooler temperatures of deep waters. An example of this are a small snail Cincinna biwaensis.

The coastal areas of the lake are also important wintering areas for waterfowl, with over 50,000 birds arriving in a typical year.
Size:
670.25 sq. km (262 sq. miles)

Habitat type:
Large Lakes

Geographic Location:

Far eastern Asia: Japan

Conservation Status:

Critical/Endangered
Local Species
Fish species include Sunayatume (Lampetra mitsukurii), Ayu (Plecoglossus altivelis), Deme-moroko (Squalidus japonica), Rhinogobius similis, and Unagi (Anguilla japonica).

Four of the fishes endemic to this lacustrine system are a Catfish (Silurus biwaensis), Isaza (Chaenogobius isaza), Honmoroko (Opsaiichthys uncirostris), and Gnathopogon caerulescens. Endemic mollusks of the genera Heterogen, Semisulcospira, Radix, Gyraulus, Anodonta, Corbicula, and Pisidium are also present in the lake.
Threats
The Lake is the largest in Japan and is relied upon to supply water for 14 million people, as well as industrial and other uses within the watershed. Although the lake is located in a protected area, it suffers from threats associated with recreational use, flood-control measures, overfishing, and eutrophication from excessive nutrient inputs. More than one-fourth of the watershed has been converted for paddy field agriculture and conifer plantations.

North American bluegills (Lepomis macrochilus) and largemouth bass (Micropterus salmoides) have come to dominate the fish community since the 1980s. These top-level predators have profoundly altered the ecosystem of the lake.

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WWF’s work

Lake Biwa - Sustainable Environment for Local Communities
This project aims to create a model for a sustainable community which will help people enjoy the natural benefits of Lake Biwa, a Global 200 Ecoregion.. To achieve this, the project aims, in partnership with local stakeholders, to renew local people’s interests and understanding of the local lake-based culture and raise awareness of the problems caused by invasive species.

WWF is encouraging a community-based conservation. It is important to raise local awareness on the importance of the lake and lake-based culture. Awareness among the residents is already quite high. Good results cab be achieved by helping concerned corporations to more actively take part in conservation by providing them with opportunities to associate their activities with nature and culture.

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