The ayu (アユ, 鮎, 年魚, 香魚) or sweetfish, Plecoglossus altivelis, is an amphidromous fish, the only species in the genus Plecoglossus and family Plecoglossidae. It is a relative of the smelts, and is placed in the order Osmeriformes. Native to the Palearctic ecozone, it occurs in rivers, lakes, and coastal waters of western Hokkaidō in Japan southward to the Korean Peninsula, China, and Hong Kong. The species has been extinct in Taiwan since 1967, although there are populations of re-introduced Japanese stocks in some of the northern streams.
The name "sweetfish" is due to the sweetness of its flesh. In reference to its typical one-year lifespan, it is also written as 年魚 ("year-fish"). The ayu is the prefectural fish of Gunma Prefecture and Gifu Prefecture.
Three subspecies are currently recognized, but their status is questioned and species may be monotypic:
Ksekino me kravyi tin boria
Ke to heri mu aplono sti fotia
Ton sophon profitia
Eleye tha me tripisun karfia
Me tin griza mu stoli mathitevo
Ke ton ayio to Theo agapo
Tin alithia nothevo
Ke stathera prohoro
Ki omos dhen pistepsa (Dhe stamato)
Orus andestepsa (Logus tha vro)
Ime o Elinas pu polema (Polema)
Ipan pos hathika (Dhe stamato)
Dhromus mu haraksan (Logus tha vro)
Emina monos mu
Ki omos epezisa
Ezisa sti fotia
I fotia sti psihi mu pu kei
Panda o kindhinos iparhi na svisti
Ap' tis pikras to meli
Pu hinete sa di vrohi
Ki omos prohorisa (Dhe stamato)
Loyia dhen honepsa (Logus tha vro)
Ime o Elinas pu prosperna (Prosperna)
Ipan na mi roto (Dhe stamato)
Logus na mi zito (Logus tha vro)
Ezisa monos mu sti fotia (Sti fotia)
Ki omos dhen pistepsa (Dhe stamato)
Orus andestepsa (Logus tha vro)
Ime o Elinas pu polema (Polema)
Ipan pos hathika (Dhe stamato)
Dhromus mu haraxan (Logus tha vro)
Emina monos mu
Ki omos epezisa
Ezisa sti fotia
(Dhe stamato)
(Logus tha vro)
Ime o Elinas pu polema (Polema)
Ipan pos hathika (Dhe stamato)
Dhromus mu haraxan (Logus tha vro)
Emina monos mu
Ki omos epezisa
Ezisa sti fotia