Ayu (fish)
| Ayu | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Ayu ( Plecoglossus altivelis ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name of the family | ||||||||||||
| Plecoglossidae | ||||||||||||
| Bleeker , 1859 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Plecoglossus | ||||||||||||
| Temminck & Schlegel , 1846 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Plecoglossus altivelis | ||||||||||||
| (Temminck & Schlegel, 1846) |
The Ayu ( Plecoglossus altivelis ) is a small smelt-like fish ( Osmeriformes ) in the monotypical East Asian family Plecoglossidae.
features
Outwardly inconspicuous at first (even the dorsal fin is hardly enlarged , contrary to the species name altivelis ), it has a number of peculiarities that distinguish it from all its close relatives (including those from the "neighboring" sub-cohort Protacanthopterygii ): it lives mainly on algae. Its dentition is particularly peculiar: it consists of 10–15 oblique rows of lamellar teeth (initially with hooked tips pointing outwards, but which are worn out) on each of the four halves of the jaw. Only the foremost teeth resemble those of the smelt, like the entire teeth of the juvenile fish. The teeth of the rows are constantly being replaced from the inside. They are attached to the jawbones (maxillary and dentals) in a relatively flexible manner by small ligaments. With them, the fish scrapes mainly blue, diatom and gold algae (“growth” including meiobenthos in it) from the bottom (gravel) of the waters in which it lives (streams, rivers, lakes, coasts), mostly by opening its mouth sideways against it presses. Of course, it also eats plankton, insect larvae, approaches, crustaceans and worms - but its ability to use algae ensures it can survive even in very oligotrophic waters (through telescoping the food chain ). Like other grazing fish, the Ayu is at least temporarily territorial and therefore quite intolerant (see e.g. Balitoridae ). The "tongue" is raised to two curved skin folds ( plecoglossus = "tongue of folds"), which produce a lot of mucus to which the food particles stick to and then be swallowed. However, the intestine is not noticeably elongated (as is usually the case with "herbivores") - only the number of pyloric tubes ( appendices pyloricae ) is high (approx. 400).
Way of life
Although the Ayu does not reach a significant size (max. 70 cm), it is one of the anadromous migratory fish , i.e. This means that it spawns in fresh water, but then lives mainly in the sea, which always offers better nutrition than rivers. Its occurrence is limited to coastal areas of the Northwest Pacific between Hokkaido and Vietnam , i.e. temperate and subtropical areas. A separate subspecies ( ryukyensis ) lives around the Ryūkyū Islands . The Ayu was successfully naturalized in Taiwan from 1925 onwards, but it was unsuccessful in Hawaii . The fry can be driven into the sea in spring, but quite a few always stay in the fresh water. There are also populations in lakes that cannot migrate to the sea at all. These fish stay smaller, but live longer if the food situation is unfavorable and spawn (at approx. 30 cm length) at the end of their life, while some of those living in the sea even take part in the spawning migration two or three times. The number of eggs stuck in a spawning pit knocked out by the female, as in trout, is a few hundred to ten thousand.
meaning
When magnified, the rows of teeth on the outside of the jaws can be seen, albeit indistinctly.
In East Asia the Ayu (English book name sweetfish ) has about the same reputation as a game fish as the salmon in Europe . The sentence “The smaller the scales, the better the fish” also applies to him - he has around 130 scales along the sidelines . That is why everything is being done in the highly industrialized countries of his home country to preserve it. Naturally, this works best with populations restricted to lakes (e.g. Lake Biwa ) (with artificial breeding, etc.). In the past, the Ayus were mainly caught during spawning in traps and baskets - and, as a tourist attraction also shown in places today, using tame cormorants ( cormorant fishing ). The fishing of the fish on a fishing rod , which is baited with a hooked conspecific, is now very popular : the Ayu is very territorial, defends its area in the river aggressively against its peers and thus causes it to get caught on the hook.
etymology
The name Ayu comes from Japanese and is usually spelled phonetically with Katakana as ア ユ . Traditionally, there are also a variety of other spellings. The most common is the kanji (Chinese characters) 鮎 , which is a combination of the characters for fish ( 魚 ) and oracle ( 占 ). Originally, however, this referred to the namazu ( Amur catfish ).
Other spellings are 年 魚 meaning “year fish” because of their one year lifespan and 香魚 meaning “scented fish” because of their fragrant slime layer. The former can also be found in the oldest Japanese works Kojiki and Nihon Shoki from the beginning of the 8th century. However, these are Jukujikun , i.e. This means that the characters used are only read as Ayu in exactly these combinations . There are also purely phonetic Kanji spellings such as 安 由 and 阿 由 .
However, these Sino-Japanese words do not reflect the meaning of the original Japanese term ayu , which is uncertain. It comes either from ayuru ( 脆 ゆ る ), which refers to the fact that it is a weak and tender fish, aya because of its beautiful shape and loveliness, from the verb ayuchiru ( 落 ち る , today ochiru , "to fall") because it falls in autumn migrates downstream, or from a for "small" and yu for "white".
Other names are Sanringyō ( 細鱗 魚 ) "small-scale fish", Ginguchigyō ( 銀 口 魚 ) "silver mouth fish" and Kunisuuo ( 国 栖 魚 ) "fish living in the country", because it is also considered an unofficial national fish.
Systematics
Because of the peculiarities of the skeleton (pelvis, caudal vertebrae) and the intestine, the Ayu is now placed in a family of its own: Plecoglossidae.
swell
- P. Adamicka: The Ayu ( Plecoglossus altivelis T. et S.), an interesting representative of the Japanese fish fauna. Österreichs Fischerei 37, 1984, pp. 140-147.
- ↑ a b c d 鮎 (あ ゆ) . In: 日本 の 旬 ・ 魚 の お 話 . Shinkō Gyorui KK, accessed September 25, 2011 (Japanese).
Web links
- Ayu (fish) on Fishbase.org (English)
- Plecoglossus altivelis inthe IUCN 2013 Red List of Threatened Species . Posted by: Huckstorf, V., 2010. Retrieved December 2, 2013.