Ayu

Ayu ( Plecoglossus altivelis )

The Ayu ( Plecoglossus altivelis ) is a small stint like fish ( Osmeriformes ) in the monotypic east Asian family Plecoglossidae.

Features

Outwardly inconspicuous at first (also the dorsal fin is altivelis contrary to the names of species hardly enlarged), it has some special features which from all his close relatives (even those from the " neighboring" sub- cohort Protacanthopterygii ) distinguished him: he lives mainly of algae. Particularly strange is his teeth: it consists of 10-15 oblique rows of lamellar teeth ( initially with hakiger tip outward, but which is worn ) on each of the four jaw halves. Only the front teeth resemble those of smelts, as even the entire dentition of juveniles. The teeth of the series are continuously replaced from the inside. They are mounted right move by small bands to the jaw bone ( maxilla and dentary ). With them, the fish scrapes predominantly blue, pebble and golden algae ( " nursery " including Meiobenthos therein) from the base (gravel ) of the water from where he lives ( streams, rivers, lakes, seashores ) by mostly sideways its mouth pressed against it. Of course, he also eats plankton, insect larvae, approach, crabs and worms - his ability to draw on algae, but it ensures the survival, even in very oligotrophic waters ( by telescoping the food - chain). Like other grazing fish, the ayu at least temporarily territorial and therefore quite incompatible (cf. Balitoridae ). The "tongue" is about two curved folds of skin increased ( Plecoglossus = " folding tongue "), which produce a lot of mucus on which the food particles from sticking to then be swallowed. The intestine is not ( as usual with " herbivores " ) extended remarkably - only the number of Pylorusschläuche ( Appendices pyloricae ) is high (about 400).

Way of life

Although the Ayu gained significant size ( max. 70 cm), he is one of the anadromous migratory fish, that is, it spawns in fresh water, but then mainly lives in the sea, which always provides better nutrition than rivers. Its occurrence is limited to coastal areas in the Pacific Northwest between Hokkaido and Vietnam, so temperate and subtropical areas. To the Ryukyu Islands lives a separate subspecies ( ryukyensis ). In Taiwan, the Ayu from 1925 has been successfully naturalized in Hawaii remained, however without success. The young fish drift into the sea in the spring, however, always remain a number in freshwater. There are also populations in lakes that can not migrate to the sea. These fish are small, but live longer with unfavorable food situation and spawn ( approximately 30 cm in length) at the end of life, while part of living in the sea, the spawning migration takes part even two or three times. The number of permanent adhesive in a like trout spawning pit lined by the female egg is a few hundred to ten thousand.

Importance

In East Asia, the Ayu (English Book name sweet fish) has about the same reputation as a game fish such as salmon in Europe. For him, the sentence " The smaller the better the scales of fish " is true - he has about 130 scales along the lateral line. Therefore, effort is made in the highly industrialized countries of his home to get him. This is best done naturally in lakes (eg Lake Biwa ) limited populations ( with artificial breeding, etc.). Formerly one began the Ayus mainly during spawning rise in pots and baskets - and shown as tourism attraction even today in places, by means of tame cormorants ( cormorant fishing). Very popular is also now the catch of the fish on the hook that is baited with a hook- reinforced counterparts: the Ayu is very territorial, defending his area aggressively against him in the river and causes so that it will hang on the hook.

Etymology

The name comes from the Japanese Ayu and is usually written phonetically with katakana asアユ. Traditionally, there are also a variety of other spellings. The most common is the Kanji (Chinese characters)鲇, which is a combination of the character for fish (鱼​​) and Oracle (占) is. Originally, however, this marked the namazu ( Amur catfish).

Other spellings are because of their one-year lifespan and香鱼in the meaning " smell fish " because of their fragrant mucus layer年 鱼in the meaning " year fish ". The former is also found in the oldest Japanese Kojiki and Nihon Shoki works from the beginning of the 8th century. However, these are Jukujikun, that is, the characters used to read these combinations as Ayu only in exact. There are also purely phonetic Kanji spellings such as安 由and阿 由.

However, these Sino- Japanese words do not give the meaning of the term urjapanischen Ayu again, which is uncertain. He comes either from ayuru (脆 ゆる), which refers to the fact that he is a weak and delicate fish, aya because of its beautiful shape and loveliness, ( "fall"落ちる, Ochiru today ) from the verb ayuchiru because he in autumn downstream migrating, or by a for "small" and yu for "white."

Other designations are Sanringyō (细鳞 鱼) " Small - Scale Fish " Ginguchigyō (银 口 鱼) " silver foot fish " and Kunisuuo (国 栖 鱼) "In the land of live fish ", because he is regarded as the unofficial national fish.

System

Due to peculiarities of the skeleton (pelvis, vertebrae of the tail ) and the intestine of the Ayu is now regarded in his own family: Plecoglossidae.

Swell

• P. Adamicka: The Ayu ( Plecoglossus altivelis T. et S. ), an interesting representative of the Japanese fish fauna. Austria Fisheries 37, 1984, pp. 140-147.