The
ayu (アユ, 鮎, 香魚) or
sweetfish,
Plecoglossus altivelis, is an
amphidromousMany types of fish migrate on a regular basis, on time scales ranging from daily to annual, and over distances ranging from a few meters to thousands of kilometers...
fishA fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins...
, the only
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
in the
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
Plecoglossus and in
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
Plecoglossidae. It is a relative of the smelts and is placed in the
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
OsmeriformesOsmeriformes is an order of ray-finned fish that includes the true or freshwater smelts and allies, such as the galaxiids and noodlefishes; they are also collectively called osmeriforms. They belong to the teleost superorder Protacanthopterygii, which also includes pike and salmon, among others...
. Native to the
PalearcticThe Palearctic or Palaearctic is one of the eight ecozones dividing the Earth surface.Physically, the Palearctic is the largest ecozone. It includes the terrestrial ecoregions of Europe, Asia north of the Himalaya foothills, northern Africa, and the northern and central parts of the Arabian...
ecozoneAn ecozone or biogeographic realm is the largest scale biogeographic division of the Earth's surface based on the historic and evolutionary distribution patterns of plants and animals...
, it occurs in rivers, lakes, and coastal waters of western
Hokkaidō, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island and the largest, northernmost of its 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaidō from Honshū, although the two islands are connected by the underwater Seikan Tunnel...
in
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
southward to the
KoreaKorea is a civilization and formerly unified nation currently divided into two states. Located on the Korean Peninsula, it borders China to the northwest, Russia to the northeast, and is separated from Japan to the east by the Korea Strait....
n Peninsula,
ChinaChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
, and
TaiwanTaiwan , also known as Formosa , is the largest island of the Republic of China in East Asia. Taiwan is located east of the Taiwan Strait, off the southeastern coast of mainland China...
.
The name "sweetfish" is due to the sweetness of its flesh.
The
ayu (アユ, 鮎, 香魚) or
sweetfish,
Plecoglossus altivelis, is an
amphidromousMany types of fish migrate on a regular basis, on time scales ranging from daily to annual, and over distances ranging from a few meters to thousands of kilometers...
fishA fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins...
, the only
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
in the
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
Plecoglossus and in
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
Plecoglossidae. It is a relative of the smelts and is placed in the
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
OsmeriformesOsmeriformes is an order of ray-finned fish that includes the true or freshwater smelts and allies, such as the galaxiids and noodlefishes; they are also collectively called osmeriforms. They belong to the teleost superorder Protacanthopterygii, which also includes pike and salmon, among others...
. Native to the
PalearcticThe Palearctic or Palaearctic is one of the eight ecozones dividing the Earth surface.Physically, the Palearctic is the largest ecozone. It includes the terrestrial ecoregions of Europe, Asia north of the Himalaya foothills, northern Africa, and the northern and central parts of the Arabian...
ecozoneAn ecozone or biogeographic realm is the largest scale biogeographic division of the Earth's surface based on the historic and evolutionary distribution patterns of plants and animals...
, it occurs in rivers, lakes, and coastal waters of western
Hokkaidō, formerly known as Ezo, Yezo, Yeso, or Yesso, is Japan's second largest island and the largest, northernmost of its 47 prefectural-level subdivisions. The Tsugaru Strait separates Hokkaidō from Honshū, although the two islands are connected by the underwater Seikan Tunnel...
in
Japanis an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, People's Republic of China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
southward to the
KoreaKorea is a civilization and formerly unified nation currently divided into two states. Located on the Korean Peninsula, it borders China to the northwest, Russia to the northeast, and is separated from Japan to the east by the Korea Strait....
n Peninsula,
ChinaChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
, and
TaiwanTaiwan , also known as Formosa , is the largest island of the Republic of China in East Asia. Taiwan is located east of the Taiwan Strait, off the southeastern coast of mainland China...
.
The name "sweetfish" is due to the sweetness of its flesh. In reference to its typical one-year life span, it is also known as
nen-gyo ("year-fish"). The ayu is
Gunma Prefectureis a prefecture of Japan located in the northwest corner of the Kantō region on Honshū island. Its capital is Maebashi.- History :The remains of a Paleolithic man were found at Iwajuku, Gunma Prefecture, in the early 20th century and there is a public museum there.Japan was without horses until...
's prefectural fish.
Ecology and uses
An
omnivoreOmnivores are species that eat both plants and animals as their primary food source...
, the ayu feeds on algae,
crustaceanCrustaceans are a very large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles...
s,
insectInsects are arthropods, having a hard exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae. They are the most diverse group of animals on the planet and include more than a million species that are already described. Insects represent more than half of all...
s,
spongeSponges are animals of the phylum Porifera . Their bodies consist of jelly-like mesohyl sandwiched between two thin layers of cells. While all animals have unspecialized cells that can transform into specialized cells, sponges are unique in having some specialized cells that can transform into...
s, and
wormThe term worm is used to describe many different distantly-related animals which have a long cylindrical body and no legs.Most animals called "worms" are invertebrates, but the term is also used for the amphibian caecilians and the slow worm Anguis, a legless burrowing lizard...
s. They are also very territorial animals. The adults ascend from coastal waters into the lower reaches of rivers to spawn in the spring. The
larvaA larva is a young form of animal with indirect development, going through or undergoing metamorphosis ....
e descend to the sea immediately on hatching and winter there before returning to fresh water again in the spring. Most but not all individuals die after their first spawning.
Ayu is an edible fish, mostly consumed in
East AsiaEast Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms. Geographically and geo-politically, it covers about , or about 28 percent of the Asian continent, about 15 percent bigger than the area of Europe, though some categorize Tibet, Xinjiang,...
. Its flesh has a distinctive, sweet flavour with "melon and cucumber aromas". It is consequently highly prized as a food fish. The main methods for obtaining ayu are by means of
fly fishingFly fishing is a distinct and ancient angling method, most renowned as a method for catching trout and salmon, but employed today for a wide variety of species including pike, bass, panfish, grayling and carp, as well as marine species, such as redfish, snook, tarpon, bonefish and striped bass...
, by using a
trapA trap is a device or tactic intended to catch an intruder or an enemy.Trap may also refer to:*Bat and trap, an old game related to cricket*Flood basalt or trap basalt, a type of rock formation*Tartrate resistant acid phosphatase , in chemics...
, 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. This method has been criticized for its cruelty towards the animal.
Japanese
anglerFishing is the activity of catching fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
s also catch it using a traditional method,
cormorant fishingCormorant fishing is a traditional fishing method in which fishermen use trained cormorants to fish in rivers. Historically, cormorant fishing has taken place in Japan, China and Macedonia, as well as other places throughout the world....
(鵜飼
ukai). On the
Nagara Riverhas played a vital role in the history of the city of Gifu, Gifu Prefecture, Japan. Throughout its long history, it evolved from a means to live, to a profitable industry, to a major tourist draw...
where
Japanese CormorantThe Japanese Cormorant , also known as Temminck's Cormorant, is a cormorant native to East Asia. It lives from Taiwan north through Korea and Japan to the Russian Far East....
s (
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 birds catch the ayu, store it in their
cropCrop may refer to:* Crop, a plant grown and harvested for agricultural use* Crop , a plant cultivated and harvested on an annual basis considered as personal property as opposed to real property. This allows a tenant farmer return for harvesting purposes even after lease of land espires. Crop may...
, and deliver it to the fishermen.
Ayu is also fished commercially in large numbers, and captive juveniles are raised in
aquacultureAquaculture is the farming of freshwater and saltwater organisms such as finfish, molluscs, crustaceans and aquatic plants. Also known as aquafarming, aquaculture involves cultivating aquatic populations under controlled conditions, and can be contrasted with commercial fishing, which is the...
before being released into rivers for sport fishing.