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Location Japan, Shiga
Central coordinates 136o 5.00' East  35o 15.00' North
IBA criteria A4i, A4iii
Area 72,224 ha
Altitude 0 - 85m
Year of IBA assessment 2004

Wild Bird Society of Japan

Site description Lake Biwako is 670 km2 and the largest lake in Japan. In addition to Northern Lake (613 km2 - average depth of 43 m) and Southern Lake (57 km2 - average depth of 4 m), which are divided by Biwakoohashi Bridge, there are many shallow marsh grounds called Naiko (inner lake) scattered around Lake Biwako, and they form habitats for wildlife connecting each other. The environmental elements are divided into two parts, a deep and vast offshore area and a shallow water zone along the coastline. The zone is rich in environment with aquatic plants such as Phragmites australis communities, sand beaches, rocky coasts and artificial banks. Surrounding areas are also agricultural fields, forests and urban areas. About 460 large and small rivers flow into Biwako, and sandbanks are well developed at the mouths of large rivers such as the Azumigawa river, the Anegawa river, the Aichigawa river and the Yasugawa river. There are five islets in the lake, Okishima, Chikubujima, Takeishima, Okinoshiroishi and the artificial Kihan-to.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Falcated Duck Mareca falcata winter  2004  present  A4i  Near Threatened 
Eurasian Wigeon Mareca penelope winter  2004  present  A4i  Least Concern 
Common Pochard Aythya ferina winter  2004  present  A4i  Vulnerable 
Tufted Duck Aythya fuligula winter  2004  present  A4i  Least Concern 
A4iii Species group - waterbirds winter  2004  min 20,000 individuals  A4iii   

IBA Monitoring

2010 medium not assessed low
Poor - based on little, or potentially unreliable/unrepresentative, data

Pollution domestic & urban waste water - type unknown/unrecorded likely in long term (beyond 4 years) majority/most of area/population (50-90%) slow but significant deterioration medium

Whole area of site (>90%) covered by appropriate conservation designation  A management plan exists but it is out of date or not comprehensive  Unknown  low 

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Biwa-ko Wetlands of International Importance (Ramsar) 65,602 protected area contained by site 65,602  
Biwako Prefectural Wildlife Protection Area 69,546 unknown 0  
Biwako Quasi National Park 97,601 unknown 0  


IUCN habitat Habitat detail Extent (% of site)
Wetlands (inland) Freshwater lakes and pools  -

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Lake Biwako. Downloaded from on 24/10/2016

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