Ayu sweetfish
Small amphidromous fish prized for its sweet flesh in East Asia.
The ayu sweetfish is a small bony fish native to East Asian rivers and coasts. It moves between salt and fresh water, living mostly one year. People value it for food and traditional fishing methods like cormorant fishing.
- Named for the sweet taste of its flesh
- Typically lives for only one year
- Caught using trained cormorants in Japan
- Scrapes algae from rocks with saw-teeth
- Prefectural fish of Gunma and Gifu
What it is
The ayu sweetfish is a small bony fish and the only member of its family. It has a slender body and saw-shaped teeth used for scraping algae. Most individuals grow to about 30 centimetres, though some reach 70 centimetres. Its flesh tastes sweet, which inspired its common name. The fish is native to East Asia and lives in both rivers and the sea.
Where it lives
This species inhabits the northwestern Pacific Ocean. Its range extends from Hokkaidō in Japan south to the Korean Peninsula, China, Hong Kong, and northern Vietnam. Wild populations in Taiwan disappeared in 1968 but were reintroduced later. Some groups live entirely in freshwater lakes like Lake Biwa, while most move between rivers and the coast.
How it lives
Ayu are omnivores that eat algae, insects, and small crustaceans. They scrape algae off rocks using their specialized teeth. Adults often defend feeding territories along riverbeds. In lakes, they tend to school together instead. They migrate downstream as larvae and return to rivers as juveniles in spring to feed and grow quickly during summer.
Breeding and life cycle
Most ayu breed in autumn in the lower parts of rivers. They dig small pits in gravel to lay eggs. Larvae hatch and drift to the sea to overwinter. Young fish return to rivers in spring. Many die after spawning once, but some survive to spawn again. Freshwater populations may spawn in spring or autumn depending on local conditions.
Fish and people
People prize ayu for its sweet flavour and melon-like aroma. It is grilled on skewers in Japanese cuisine. Fishermen use fly fishing, traps, or decoy fish to catch them. Cormorant fishing on the Nagara River is a famous cultural tradition where trained birds catch the fish. Juveniles are also raised in captivity for sport fishing stocks.
Status and threats
The Ryukyu subspecies is considered endangered. Wild ayu in Taiwan went extinct due to pollution but have been restocked. Other populations face threats from habitat changes, but many remain stable. Conservation efforts include stocking reservoirs and protecting river habitats for breeding grounds.
Questions people ask about Ayu sweetfish
Why is it called sweetfish?
The name comes from the distinctively sweet flavour of its meat. People often describe the taste as having aromas similar to melon or cucumber. This unique flavour makes it a prized food fish in East Asian cuisine.
How long does an ayu live?
Most ayu live for only one year, which is why it is sometimes called year-fish. However, some individuals survive for two or three years. Those that live longer may spawn multiple times before dying.
What do ayu eat?
They are omnivores that primarily feed on algae growing on rocks. They use their saw-shaped teeth to scrape this algae off surfaces. They also eat insects, crustaceans, sponges, and worms found in their river habitats.
Where can you find ayu?
Ayu are native to East Asia. They live in rivers and coastal waters from Hokkaidō in Japan down to northern Vietnam. Some populations live entirely in freshwater lakes, while most migrate between rivers and the sea.
Good reading and sources
- Ayu sweetfish on WikipediaEncyclopedia
- More photos on Wikimedia CommonsPhotos
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Ayu sweetfish", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
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