Biwa trout

{{Short description|Species of fish}} {{Speciesbox | name = Biwa trout | image = Oncorhynchus masou rhodurus.jpg | taxon = Oncorhynchus biwaensis | authority = Fujioka ''et al.'' 2025 }}

The '''Biwa trout''', or '''Biwa salmon''' (''Oncorhynchus biwaensis'')<ref name=":0">{{Cite journal |last=Fujioka |first=Yasuhiro |last2=Kuwahara |first2=Masayuki |last3=Tabata |first3=Ryoichi |last4=Fuke |first4=Yusuke |last5=Nakabo |first5=Tetsuji |date=2025-06-21 |title=The Biwa salmon, a new species of Oncorhynchus (Salmonidae) endemic to Lake Biwa, Japan |url=https://doi.org/10.1007/s10228-025-01032-z |journal=Ichthyological Research |language=en |doi=10.1007/s10228-025-01032-z |issn=1616-3915|url-access=subscription }}</ref> 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.<ref>{{Cite journal |last=Jordan |first=David Starr |last2=Jordan |first2=David Starr |last3=Hubbs |first3=Carl L. |last4=McGregor |first4=Ernest Alexander |date=1925-06-27 |title=Record of fishes obtained in Japan by David Starr Jordan in Japan, 1922 |url=https://www.biodiversitylibrary.org/part/234844 |journal=Memoirs of the Carnegie Museum |volume=10 |issue=2 |pages=93––346 |doi=10.5962/p.234844|doi-access=free }}</ref> However, The Biwa trout was found to be a separate species from ''O. rhodurus'' and was described as a new species in 2025.<ref name=":0" /> ''O. rhodurus'' may represent a hybrid specimen instead.<ref>{{Cite web |last=宏 |first=瀬能 |date=2008 |title=境界線上で翻弄される箱根の魚たち |url=https://nh.kanagawa-museum.jp/www/pdf/tobira54_3senou.pdf |website=Kanagawa Prefectural Museum of Natural History |access-date=2025-06-30 |archive-date=2025-06-30 |archive-url=https://web.archive.org/web/20250630135732/https://nh.kanagawa-museum.jp/www/pdf/tobira54_3senou.pdf |url-status=dead }}</ref>

Biwa trout is found only in the waters of northern Lake Biwa, and feeds on plankton, freshwater prawns, aquatic insects, worms, ''ayu'' and other small fishes, and sometimes small mammals. Adult Biwa trout usually range from {{cvt|40|to|50|cm}} in length and {{cvt|1.5|to|2.5|kg}} in weight, although large specimens can be up to {{cvt|70|cm}} long and {{cvt|5.0|kg}} in weight.

==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.

<gallery widths="120px" heights="120px" mode="packed"> 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 </gallery>

==References== * {{FishBase species alt|4731|taxon=''Oncorhynchus rhodurus''|year=2010}} {{Reflist}}

==External links== *Yoshikazu Fujioka [http://www.hi-ho.ne.jp/amago/trout/biwamasu2.html Profile of Biwamasu] Trout and Seasons of The Mountain Village. www.hi-ho.ne.jp * [https://web.archive.org/web/20070505050021/http://www.nies.go.jp/biodiversity/invasive/detail/50860.html Biwa trout information from the National Institute for ES of Japan (Japanese)] * [https://web.archive.org/web/20061201045002/http://members.aol.com/user231961/biwa.htm Fishing info. of Biwa trout (Japanese - at Archive.org)]

Category:Oncorhynchus Category:Endemic fish of Japan Category:Freshwater fish of Japan Category:Fish described in 1925 Category:Taxa named by David Starr Jordan