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: 118.

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 400 000 years ago.

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

Uses:

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 sp.). 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', 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 buergeri 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 reinii). 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.
'Biwakogata Sujishimadojou', a loach (Cobitis minamorii oumiensis). Habitat is the lakeshore areas and rivers of the Lake Biwa region, but recently numbers have dramatically decreased.
'Ohgata Sujishimadojou', a loach (Cobitis magnostriata). Habitat is the lakeshore areas and rivers of the Lake Biwa region, but recently numbers have dramatically decreased.
'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', a 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', a 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. This species reaches 255mm across. It played an important role 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', a water plant (Vallisneria asiatica var. biwaensis). The leaves have a characteristic twist along their length.
'Sannenmo', a water plant (Potamogeton biwaensis). The leaves don't have a stalk, and are linear with a pointed tip.
Plankton
'Biwakunshoumo', an algae (Pediastrum biwae). In Japanese this species is called 'the decoration' due to its shape.
'Biwatsubokamuri', an Amoebozoa (Difflugia biwae). By swallowing sand grains this amoeba produces a hard shell.