Ayu

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This article is about the fish. For other uses, see Ayu (disambiguation).
Ayu
Sweetfish, Plecoglossus altivelis.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Superclass: Osteichthyes
Class: Actinopterygii
Subclass: Neopterygii
Infraclass: Teleostei
Superorder: Protacanthopterygii
Order: Osmeriformes
Suborder: Osmeroidei
Superfamily: Osmeroidea
Family: Plecoglossidae
Genus: Plecoglossus
Temminck & Schlegel, 1846
Species: P. altivelis
Binomial name
Plecoglossus altivelis
(Temminck & Schlegel, 1846)

The ayu (アユ, 鮎, 年魚, 香魚?) or sweetfish, Plecoglossus altivelis, is a species of fish. It is the only species in the genus Plecoglossus and family Plecoglossidae. It is a relative of the smelts and other fish in the order Osmeriformes.

Native to East Asia, it is distributed in the northwestern Pacific Ocean along the coast of Hokkaidō in Japan southward to the Korean Peninsula, China, Hong Kong and northern Vietnam. It is amphidromous, moving between coastal marine waters and freshwater lakes and rivers. A few landlocked populations also exist in lakes such as Biwa. It is an introduced species in Taiwan.[1]

The name "sweetfish" was inspired by the sweetness of its flesh. In reference to its typical one-year lifespan, it is also written as 年魚 ("year-fish").[2] Some individuals live two to three years.[1] The ayu is the prefectural fish of Gunma Prefecture and Gifu Prefecture.[3]

Subspecies[edit]

Two[4] to three[5] subspecies are recognized by some authors. Others do not distinguish the subtaxa.[6]

Subspecies include:

  • P. a. altivelis (Temminck & Schlegel, 1846) (ayu, sweetfish)
  • P. a. chinensis Y. F. Wu & X. J. Shan, 2005 (Chinese ayu)
  • P. a. ryukyuensis M. Nishida, 1988 (Ryukyu ayu-fish) – endangered[7]

Biology[edit]

An omnivore, the ayu feeds on algae, crustaceans, insects, sponges, and worms. It feeds on algae that accumulates on the rocks, scraping it off the rocks with their saw-shaped teeth.[2][8]

This is a migratory fish. It lives along the coast between autumn and spring. It enters the rivers to breed, and while some die afterwards, many return to the ocean. Larvae are carried downriver to the sea, where they grow and develop.[1] Some populations can be found in lakes, where they remain their entire lives.[1] They are also stocked in reservoirs.[1]

Human uses[edit]

Ayu is an edible fish, mostly consumed in East Asia. Its flesh has a distinctive, sweet flavour with "melon and cucumber aromas".[9] It is consequently highly prized as a food fish. The main methods for obtaining ayu are by means of fly fishing, by using a fish trap, and by fishing with a decoy which is known as ayu-no-tomozuri in Japan. The decoy is a living ayu placed on a hook, which swims when immersed into water. It provokes the territorial behavior of other ayu, which assault the "intruder" and get caught.[10]

Japanese fishers also catch it using a traditional method, cormorant fishing (鵜飼 ukai). On the Nagara River where Japanese cormorants (Phalacrocorax capillatus) are used by the fishermen, the fishing season draws visitors from all over the world. The Japanese cormorants, known in Japanese as umi-u (ウミウ, "sea-cormorant"), are domesticated birds trained for this purpose. The bird catches the ayu, stores it in its crop, and delivers it to the fishermen.[11]

Ayu is also fished commercially, and captive juveniles are raised in aquaculture before being released into rivers for sport fishing.

A common method of preparing ayu and other small fish in Japan is to skewer it in such a way so that its body forms a wave, making it look as though it is swimming.[12]

Gallery[edit]

References[edit]

  1. ^ a b c d e f Huckstorf, V. 2012. Plecoglossus altivelis. The IUCN Red List of Threatened Species. Downloaded on 18 February 2016.
  2. ^ a b Queen of Freshwater Streams. Food Forum. Kikkoman Global Website.
  3. ^ Symbols of Gifu Prefecture. Gifu Prefectural Government.
  4. ^ Froese, R. and D. Pauly, Editors. Plecoglossus. FishBase. 2015.
  5. ^ Shan, X., Wu, Y., & Kang, B. (2005). Morphological comparison between Chinese Ayu and Japanese Ayu and establishment of Wu & Shan subsp. nov. Journal of Ocean University of China (English Edition), 1(4), 61-66.
  6. ^ Froese, R. and D. Pauly, Editors. Plecoglossus altivelis altivelis. FishBase. 2015.
  7. ^ World Conservation Monitoring Centre 1996. Plecoglossus altivelis ryukyuensis. The IUCN Red List of Threatened Species. Downloaded on 5 November February 2016.
  8. ^ "Rock Fishing in Tokushima, Japan". USA Today. 
  9. ^ Gadsby, P. The chemistry of fish. Discover Magazine 25 November 2004.
  10. ^ Waldman, J. (2005). 100 Weird Ways to Catch Fish (1st ed.). Mechanicsburg, PA: Stackpole Books. pp. 6–7. ISBN 0811731790. 
  11. ^ Cormorant-Fishing on the Nagara River. Gifu Rotary Club.
  12. ^ No. 2: Ayu fish. Hiroko's Kitchen. 10 August 2010.

Further reading[edit]

  • Takeshima, Hirohiko; Iguchi, Kei-ichiro & Nishida, Mutsumi (2005): Unexpected Ceiling of Genetic Differentiation in the Control Region of the Mitochondrial DNA between Different Subspecies of the Ayu Plecoglossus altivelis. Zool. Sci. 22(4): 401–410. doi:10.2108/zsj.22.401 (HTML abstract)

External links[edit]