The Biwa trout (''Oncorhynchus rhodurus'') is an

anadromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousan ...

salmonid Salmonidae is a family of ray-finned fish that constitutes the only currently extant family in the order Salmoniformes . It includes salmon (both Atlantic and Pacific species), trout (both ocean-going and landlocked), chars, freshwater whitefis ...

fish of the genus ''

Oncorhynchus ''Oncorhynchus'' is a genus of fish in the family Salmonidae; it contains the Pacific salmon and Pacific trout. The name of the genus is derived from the Greek ὄγκος (ónkos, “lump, bend”) + ῥύγχος (rhúnkhos, “snout”), in r ...

'',

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Lake Biwa is the largest freshwater lake in Japan, located entirely within Shiga Prefecture (west-central Honshu), northeast of the former capital city of Kyoto. Lake Biwa is an ancient lake, over 4 million years old. It is estimated to be the 13th ol ...

Shiga Prefecture is a prefecture of Japan located in the Kansai region of Honshu. Shiga Prefecture has a population of 1,412,916 (1 October 2015) and has a geographic area of . Shiga Prefecture borders Fukui Prefecture to the north, Gifu Prefecture to the nort ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, but also introduced to

Lake Ashi , also referred to as Hakone Lake or Ashinoko Lake, is a scenic lake in the Hakone area of Kanagawa Prefecture in Honshū, Japan. It is a crater lake that lies along the southwest wall of the caldera of Mount Hakone, a complex volcano that last ...

and

Lake Chūzenji , also called Sea of Happiness, is a scenic lake in Nikkō National Park in the city of Nikkō, Tochigi Prefecture, Japan. It was created 20,000 years ago when Mount Nantai (2484 m) erupted and blocked the river. The lake has a surface area of 11. ...

. While called

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salmoni ...

, the fish is most closely related to the

masu salmon The masu salmon (''Oncorhynchus masou''), also known as masu ( ja, マス, , trout) or in Japan, is a species of salmon belonging to the genus ''Oncorhynchus'', found in the North Pacific along Northeast/East Asian coasts from the Russian Far Eas ...

(''Oncorhynchus masou'') of the western

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

, and is most often considered a subspecies of it, ''Oncorhynchus masou rhodurus''. ''rhodurus, Oncorhynchus''
In: W. Eschmeyer:

Catalog of Fishes Catalog of Fishes is a comprehensive on-line database and reference work on the scientific names of fish species and genera. It is global in its scope and is hosted by the California Academy of Sciences. It has been compiled and is continuously up ...

Online Database. California Academy of Sciences. Downloaded 16 Feb 2015 Biwa trout is found only in the waters of northern Lake Biwa, and feeds on

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

, freshwater

prawn Prawn is a common name for small aquatic crustaceans with an exoskeleton and ten legs (which is a member of the order decapoda), some of which can be eaten. The term "prawn"Mortenson, Philip B (2010''This is not a weasel: a close look at nature ...

aquatic insects Aquatic insects or water insects live some portion of their life cycle in the water. They feed in the same ways as other insects. Some ''diving'' insects, such as predatory diving beetles, can hunt for food underwater where land-living insects ca ...

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wor ...

s, ''

ayu Ayu or AYU may refer to: * Ayu (given name) * Ayu sweetfish (''Plecoglossus altivelis''), a species of smelt * ''Ayu'', a local name for the African manatee * Ayu (singer) or Ayumi Hamasaki, Japanese singer * Ayu Islands, a small archipelago in I ...

'' and other small fishes, and sometimes small mammals. Adult Biwa trout usually range from in length and in weight, although large specimens can be up to long and in weight.

Use as food

Biwa trout represents a unique

food fish Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is ingest ...

for the Shiga Prefecture. Biwa trout and its

caviar Caviar (also known as caviare; from fa, خاویار, khâvyâr, egg-bearing) is a food consisting of salt-cured roe of the family Acipenseridae. Caviar is considered a delicacy and is eaten as a garnish or a spread. Traditionally, the ter ...

are considered a delicacy. Usual ways to prepare the trout is as

sashimi is a Japanese delicacy consisting of fresh raw fish or meat sliced into thin pieces and often eaten with soy sauce. Origin The word ''sashimi'' means "pierced body", i.e. "刺身" = ''sashimi'', where 刺し = ''sashi'' (pierced, stuck) ...

, by

grilling Grilling is a form of cooking that involves dry heat applied to the surface of food, commonly from above, below or from the side. Grilling usually involves a significant amount of direct, radiant heat, and tends to be used for cooking meat a ...

with salt, in meuniere, or by

smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...

deep-frying Deep frying (also referred to as deep fat frying) is a cooking method in which food is submerged in hot fat, traditionally lard but today most commonly oil, as opposed to the shallow oil used in conventional frying done in a frying pan. Nor ...

simmering Simmering is a food preparation technique by which foods are cooked in hot liquids kept just below the boiling point of water (lower than ) and above poaching temperature (higher than ). To create a steady simmer, a liquid is brought to a boil, ...

, ''etc''. The fish has a reputation as being very difficult to catch by

angling Angling is a fishing technique that uses a fish hook or "angle" (from Old English ''angol'') attached to a fishing line to tether individual fish in the mouth. The fishing line is usually manipulated via a fishing rod, although rodless techniqu ...

References

External links

*Yoshikazu Fujiok
Profile of Biwamasu
Trout and Seasons of The Mountain Village. www.hi-ho.ne.jp

* ttps://web.archive.org/web/20061201045002/http://members.aol.com/user231961/biwa.htm Fishing info. of Biwa trout (Japanese - at Archive.org) Oncorhynchus Endemic fauna of Japan Freshwater fish of Japan Fish described in 1925 {{Salmoniformes-stub