Lake Biwa Facts

alternatetext Size: 674 square km.

Volume: Total 27.5 cubic km.

Max depth: Mean depth:
Length of shoreline: 235 km.

Catchment area: 3174 square km.

No. of inlets: approx. 340.

No. of natural outlets: one (the Seta River).

Trophic status:

Age: There has been a continuous presence of a lake in the area for approximately one million years, since the formation of Lake Biwa's predecessor, Lake Katata. Lake Katata gradually moved to the west to the present position of the southern basin of Lake Biwa, and then expanded north-east, forming the current north basin about 430 000 years ago.

However, to the south east of Lake Biwa there were four other lakes that existed back to about 3.5 million years ago. Due to its age, Lake Biwa is classified as one of the world's few 'ancient' lakes.

Uses:
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Conservation Status:
No. of Species living in Lake: 595 animals, 491 plants.

No. of endemic species/subspecies: 62, including:

Some of the endemic species/subspecies are listed below:

Fish
'Honmoroko'
A minnow
Gnathopogon caerulescens
Habitat is deep open water. This fish is prized for its taste when grilled.
'Gengorobuna'
Japanese crucian carp
Carassius cuvieri
Habitat is middle to surface waters. The Japanese name of this fish relates to a famous local legend.
'Biwamasu'
Biwa Salmon
Oncorhynchus masou subsp.
Habitat is cool middle waters. Prized for its lean, tasty flesh.
'Isaza'
A goby
Gymnogobius isaza
It spends the daytime at depths of 30m or more, coming to the surface at night.
'Biwako-ohnamazu'
Giant Lake Biwa Catfish
Silurus biwaensis
Habitat is the bottom of the lake. This is the largest fish in the lake.
'Biwahigai'
Biwa oily gudgeon
Sarcocheilichthys variegatus microoculus
Habitat is sand and gravel. This species lays its eggs in clams.
'Nigorobuna'
A crucian carp
Carassius auratus grandoculis
Habitat is fairly deep water. The juvenile fish grow in reed beds. It is used for 'funazushi', a local dish of fermented fish.
'Wataka'
A carp
Ischikauia steenackeri
Habitat is middle to surface waters. It eats plants and in Japanese is also known as the 'horse fish'.
'Utsusemikajika'
A sculpin
Cottus reini
This species is found in Lake Biwa and the surrounding rives of the drainage basin.
'Biwayoshinobori'
A goby
Rhinogobius sp.
This endemic species was first reported in 1998. It lives in the open waters of the lake, coming closer to shore during the summer to lay eggs.
'Sugomoroko'
A minnow
Squalidus chankaensis biwae
Until recently, this species was considered to be the same as a species found in other parts of Japan, but research has determined that the Lake Biwa specimens are a separate subspecies.
'Aburahigai'
A minnow
Sarcocheilichthys biwaensis
Habitat is rocky areas of the lake, but recently its numbers have dramatically decreased.
'Sujishimadojou'
A loach
Cobitis sp. 2, subsp. 4
Recently one species has been reclassified into three species and eight subspecies. This is a small subspecies that lives in rivers draining into the lake.
'Sujishimadojou'
A loach
Cobitis sp. 1
Recently one species has been reclassified into three species and eight subspecies. This is a large species that lives in Lake Biwa and river mouths.
'Iwatoko-namazu'
Biwa rock catfish
Silurus lithophilus
Inhabits the rocky areas of the north of the lake. Of the three species of catfish living in Lake Biwa, this one is said to be the most tasty.

Molluscs
'Biwakomizushitadami'
Gastropod
Biwakovalvata biwaensis
Lives at depths ranging from 2 to 80m on muddy sediments, but can also be found on gravel in the north basin. The diameter of the shell is 3 to 5mm.
'Nagatanishi'
Gastropod
Heterogen longispira
Lives at depths ranging from 2 to 30m. It has become rare in the south basin. It is a large species, with a shell reaching 70mm in length.
'Ikechougai'
Biwa pearly mussel
Hyriopsis schlegeli
Habitat is sandy mud at depths of 1 to 5m. Of the two species of this group that live in Japan, this one is the largest, reaching 255mm across. Used to be important in the freshwater pearl industry.
'Setashijimi'
The Seta clam
Corbicula sandai
Can be found throughout the lake at depths of 2 to 30m. Size ranges from 20 to 35mm. It is eaten by local people.

Water plants
'Nejiremo'
Water plant
Vallisneria asiatica var. biwaensis
The leaves have a characteristic twist along their length.
'Sennenmo'
Water plant.
Potamogeton biwaensis
The leaves don't have a stalk, and are linear with a pointed tip.

Plankton
'Biwakunshoumo'
Algae
Pediastrum biwae
In Japanese this species is called 'the decoration' due to its shape.
'Biwashibokamuri'
Amoebozoa
Difflugia biwae
By swallowing sand grains this amoeba produces a hard shell.