The Lake Biwa Museum's aquarium is one of the largest freshwater aquarium facilities in Japan, and features fishes and other aquatic organisms from Lake Biwa, its watershed, and several other lakes of the world. A variety of endangered fish species from Japan are bred in the aquarium's Fish Conservation and Breeding Center, as part of a national collaborative effort among several zoos and aquariums to conserve these species and, in some cases, save them from imminent extinction.
Lake Biwa; Reed Marsh Habitat
Reed marshes, characterized by the abundance of reeds and other emergent plants, are still present around the lake shore, although in many areas they have been destroyed by land reclamation and development activities. These habitats are inhabited by a highly diverse and abundant fauna. This outdoor tank accommodates 13 species of fish, including carps, bitterlings and gudgeons and two species of freshwater mussels.
It should be noted that this is how the fish community looked up until 35 years ago. Invasive species, such as largemouth bass and bluegill now dominate such communities.
Lake Biwa; Rocky Shore
The tunnel tank represents rocky shore and offshore habitats around Chikubu Island in the northern part of Lake Biwa.
In this tank are piscivorous chub and crucian carps, which prefer to swim in surface to mid-waters, and the rock catfish and Japanese eel, which prefer to remain close to the bottom.
The walls of the tunnel tank are made from acrylic plastic almost 16cm thick!
Lake Biwa; The Biwa Catfish
Known as the guardian spirit of Lake Biwa, the endemic Biwa catfish is the largest fish in the lake. It can grow up to 1.2 m in length and weigh over 10 kg.
It is a nocturnal predator, spending the day at over 40 m depth and coming up to the shallower water at night to prey on smaller fish.
Lake Biwa; Ko-Ayu
Although small in size, the ko-ayu, or lake ayu, is one of the most abundant fish in Lake Biwa, and also comprises the highest-value fishery in the lake.
The ko-ayu spawns either in rivers or on wave-washed pebble beaches along the lake shore.
Lake Biwa; Cold-Water Biwa Salmon
The Biwa Salmon is a land-locked subspecies endemic to the lake. They live in the deep pelagic zone of the lake where the water is around 15 degrees C. Spawning takes place in the middle reaches of rivers during October to November when the fish reach 3 to 5 years old.
Due to the destruction of the natural river systems around the lake, the population of Biwa salmon is now maintained through artificial propagation in hatcheries.
Lake Biwa; Littoral Zone
In the nearshore area aquatic plants are abundant and are used as shelter and as nurseries by many organisms. especially small fish and invertebrates. Examples include freshwater snails, the Japanese trident goby, the Japanese ricefish, the golden venus chub, the lake prawn and the Oriental river prawn.
Lake Biwa; Fish with Unusual Habits
There are several species of fish in Lake Biwa that lay their eggs within the shells of living mussels. As the females use their long spawning tube to place eggs into the inhalent siphon of the mussel, the male releases sperm to fertilize them.
Other fish with unusual habits include the forktail bullhead catfish, which makes sounds to communicate threat and the silver crucian carp, a female subspecies of fish that can reproduce without any genetic contribution by a male.
Lake Biwa; Alien Species
Many species from different parts of the world have been introduced into Japan, and in particular Lake Biwa. These include the northern snakehead, the red swamp crayfish and the water hyacinth.
The two most destructive species are the largemouth bass and bluegill sunfish. Both were introduced for sport fishing and/or as a source of food, but have bred uncontrollably in the lake resulting in the near disappearance of several endemic species.
Aquatic Life of Streams and Ponds
Recent changes to lowland waters in much of Japan has resulted in some once common species becoming endangered. These include the predatory diving beetle, the water scorpion and the giant water bug, which used to be common in ponds and irrigation ditches.
Faunas from different stretches of rivers are also displayed. Species from middle reaches of rivers include the Japanese giant salamander, dark chub, pale chub, dace, gudgeons, minnows and barbels. Freshwater crabs, scuplins, catfish and loaches can be found in the upper reaches of rivers.
Within Japan, many freshwater fish species have declined drastically in number owing to the effects of man; pollution, habitat alteration and destruction, overfishing and the introduction of alien species. Some of these fish are kept and bred at the museum for conservation.
For two species, however, conservations measures are too late. The Amur ninespine stickleback and the black kokanee salmon are now both extinct in Japan.
The Touching Corner
Near the exit of the aquarium is the touching corner. Here children, while closely supervised and helped by museum staff, can touch crayfish and small crucian carps. They can also put their hands into the contact tank through the holes in the front of the glass.
This exhibit was renovated with the help of the Lake Biwa Fish Network, a local community group.
Fish from Other Lakes in the World
The museum also houses fish from other lakes in the world. These include fish from Lake Tanganyika (East Africa), Lake Dongting-hu (China), Tonle Sap (Cambodia) and the Laurentian Great Lakes (North America).
Some of the largest fish in the museum are also the oldest. Sturgeons and gars are representatives of ancient fish, groups that have survived relatively unchanged for tens of millions of years.
Lakes and People around the World
Just outside the aquarium several exhibits compare the natural environments of a variety of lakes around the world, and the lifestyles of the people living in the regions surrounding these lakes. These include Lake Dongting (China), Lake Baikal (Russia), Lake Geneva and Lake Constance (Europe), Lake Tanganyika (East Africa), the Laurentian Great Lakes (North America) and Lake Titicaca (South America).
By making comparisons among these and other lakes we can expand our understanding of lake biology and lakeshore cultures in other parts of the world.
List of Exhibits
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