Biwa trout

 ( Oncorhynchus ) 

The Biwa trout, or Biwa salmon ( Oncorhynchus biwaensis) is an anadromous salmonid fish of the genus Oncorhynchus, endemic to Lake Biwa in Shiga Prefecture, Japan, but also introduced to Lake Ashi and Lake Chūzenji.

This species was previously identified to be same animal as Oncorhynchus ( masuou) rhodurus which is first described from Lake Ashi. However, The Biwa trout was found to be a separate species from O. rhodurus and was described as a new species in 2025. O. rhodurus may represent a hybrid specimen instead.

Biwa trout is found only in the waters of northern Lake Biwa, and feeds on plankton, freshwater , aquatic insects, , Ayu sweetfish 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.

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Use as food Biwa trout represents a unique food fish for the Shiga Prefecture. Biwa trout and its caviar are considered a delicacy. Usual ways to prepare the trout is as sashimi, by grilling with salt, in meuniere, or by smoking, deep-frying or simmering, etc. The fish has a reputation as being very difficult to catch by angling.

File:Grilling with salt-rhodurus.jpg|Grilled File:20240714 biwamasubutteryakiju.jpg|Grilled with rice File:20240714 biwamasutirasizusihuju.jpg|Raw chirashizushi with rice File:Rhodurusっ子（魚卵）のしょうゆ漬.JPG|Roe pickled in soy sauce

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External links

• Yoshikazu Fujioka Profile of Biwamasu Trout and Seasons of The Mountain Village. www.hi-ho.ne.jp
• Biwa trout information from the National Institute for ES of Japan (Japanese)
• Fishing info. of Biwa trout (Japanese - at Archive.org)

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