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A nigorobuna of Lake Biwa

Nigoro-buna, sometimes called round crucian carp, is a type of wild goldfish (Carassius auratus) endemic to Japan. Its habitat is limited to Lake Biwa, its tributaries and distributaries, and irrigation canals, in the Shiga Prefecture (west-central Honshu), northeast of Kyoto.

The fish is of culinary importance locally in Shiga Prefecture, where it is used as an ingredient for funazushi, a type of narezushi. The fermented fish is closely packed with rice and salt in tubs.


The Japanese name nigorobuna (ニゴロブナ) is ascribed to various etymologies. One has it that it earned the name ni-gorō-buna (Japanese: 似五郎鮒) meaning "gorō-buna's look-alike", because once it reaches sizes of approximately 1.2–1.3 feet, it begins to look confusingly similar to the gengorō-buna (源五郎鮒), C. cuvieri, the wild form of the Japanese crucian carp, a closely related species also endemic to the lake.[1] It is alternatively styled nigorobuna , which crudely translates to "braising-timely-carp".


Some literature refer to nigorobuna as subspecies Carassius auratus grandoculis,[2] but this subspecies is not generally recognized.[3]


A typical adult nigorobuna attains 35 cm (14 in)[4] length at maturity. Its shape resembles the nagabuna[a] that populate Lake Suwa; its body depth is short, and breadth is wide.[5]

The head is large, with a ventricular contour that is characteristically ridged.[5] The mouth slit is slanted upwards.[5] Around 61 (or 52–72) gill rakers can be counted, and the dorsal fin rays consist of one spine and 17 (or 15 to 18) soft rays. The anal fin has one spine and five soft rays.[5] The basal length of the dorsal fin is rather long.[5] The total length is 2.7x[5] the body depth.


Larvae and juveniles are found on the surface and medium depths entrenched within reeds[5] around the lake, in other words, inlets rich in aquatic plants.[6] Adults occupy shallower waters in summer and move to deeper waters during the cold winter.

One study showed that when larvae of about 1 cm length were compared, nigorbuna was "scarce(ly)" feeding on algae, compared with local genogoro-buna, which had 25–50% algal digestive tract content by bulk.[7] The fish showed a preference for certain water fleas over another, relying heavily on Chydorus spp. ( Data related to Chydorus at Wikispecies) and to a lesser extent on Mesocyclops. By contrast, the gengoro-buna kept in the same enclosure preferred rotifer spp. The fry (larvae) of both species largely ignored other types of zooplankton (such as Alona, Scapholeberis, and copepodid larvae) which were plentiful.[8] As they grow into juveniles exceeding 1 cm, the nigorobuna begin pecking at aquatic plants to feed on attached algae, so by the time they attain 2 cm lengths,[5] algae (and rotifers, small percentage) account for half their diet.[9] When they grow larger, they capture somewhat bottom-dwelling zooplankton.[5]

Adults spawn from April to June, laying eggs on aquatic plants when water levels rise due to the rainy season.[5] The hatchlings live by the reedy shore, and move offshore as they grow, reaching full size in 2 to 3 years.[10]


Funa-zushi made from "nigoro crucian carp": Females carrying roe (pictured) are especially prized.

This is a highly prized fish commercially, made into funazushi, where whole fish are salted and fermented in beds of cooked rice. An authentic funazushi traditionally must use the "round crucian carp", and for this reason it has been dubbed sushi-buna meaning "the crucian carp for sushi". The dish, a type of narezushi, is a local delicacy of Shiga Prefecture, and known for its pungent odor.[11][12]

This species is said to make superior funazushi that is tender down to the bones, in contrast to imitations made by using gengoro-buna (Carassius cuvieri) as a substitute.[13] The ginbuna (Carassius auratus langsdorfii is also said to be used as a substitute.

Fishing regulations[edit]

The annual catch was estimated to be 500 tons in 1965, fell to 178 tons by 1989, and drastically down to 18 tons by 1997[10] so that efforts were begun to release fishery-raised spawn into nearby rice paddies connected with the water system.[10] Nowadays, the species is also farmed in Saitama Prefecture.[14]

Shiga Prefecture, in its announced project to recover the fish stock, promulgated rules through its Lake Biwa Fisheries Management Commission, effective April 1, 2007, prohibiting the capture of fish measuring 22 cm or less.[15]

The devastation of numbers is blamed on habitat loss, as well as the introduction of nuisance alien species such as black bass and bluegill into the Lake.


  1. ^ The MOE Red databook gave "subspecies 1", and Fishbase (version of 2006), which gives subspecies C. a. buergeri. But Fishbase no longer list this subspecies.


  1. ^ Hitomi, Hitsudai, d. 1701 (1981), Yoshii, Hatusko; Shimada, Isao, eds., Honchō shokkan 本朝食鑑, 5, Heibonsha, p. 267, ASIN B000J80JPO, 又此魚ノ大ナルモノ、一尺二三寸位ナルモノハ源五郎鮒二似タリテ、故ニ似五郎ト呼ブト云フ説ヲ優レリトス
  2. ^ e.g., Fujioka, Y. (1997). Production and some properties of gynogenetic diploids in nigorobuna crassius carassius grandoculi. Bull. Shiga. Prefect. Fis. Exp. Stn. 46, 108 (ja icon), citeby Arai, Katsutoshi (2001) Genetic improvement of aqualculture finfish species by chromosome manipulation techniques in Japan".
  3. ^ Froese, Rainer and Pauly, Daniel, eds. (2006). "Carassius cuvieri" in FishBase. April 2006 version.
  4. ^ Gomei & Furukawa 2005Shokuzai kenko daijiten", p.303 gives 35-40cm (13¾-15¾ inches)
  5. ^ a b c d e f g h i j NIES 2012(website) citing Kawanabe 2002 (Ninon no tansuigyo = fresh water fishes of japan)
  6. ^ Hirai 1969
  7. ^ Hirai., Naofusa, (1969). Japanese Shinto. International Society for Educational Information, Inc. OCLC 12931200.
  8. ^ Hirai 1969, p. 124, Tables 1
  9. ^ Hirai 1969, p. 124, Tables 2
  10. ^ a b c Fisheries Management Division 2007
  11. ^ Kawanabe, Hiroya; Coulter, George W.; Roosevelt, Anna Curtenius (1999), Ancient Lakes: Their Cultural and Biological Diversity, Kenobi Productions, p. 228
  12. ^ Kawanabe, Hiroya; Nishino, Machiko; Maehata, Masayoshi (2012), Lake Biwa: Interactions between Nature and People, Springer Science & Business Media, p. 346
  13. ^ Gomei & Furukawa 2005, p.303
  14. ^ Kuzushima, Kazumi (葛島一美); Kumagai, Masahiro (熊谷正裕) (2011). Nihon tanago tsuri kikō 日本タナゴ釣り紀行. Tsuribito-sha. ISBN 9784885361883., p.40
  15. ^ Lake Biwa Fisheries Management Commission 2007